Non-aqueous compositions containing nanosized particles of monoazo laked pigment

ABSTRACT

Non-aqueous disperson compositions, such as ink compositions, contain a polymeric dispersant, a polymeric resin, an organic liquid, and a nanoscale pigment particle composition including an organic monoazo laked pigment including at least one functional moiety, and a sterically bulky stabilizer compound including at least one functional group, wherein the functional moiety of the pigment associates non-covalently with the functional group of the stabilizer; and the presence of the associated stabilizer limits the extent of particle growth and aggregation, to afford nanoscale-sized pigment particles.

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/759,913 to Rina Carlini et al. filed Jun. 7, 2007, theentire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure is generally directed to non-aqueous compositionscontaining nanoscale pigment particle compositions. More specifically,this disclosure is directed to non-aqueous compositions containingdispersions of organic mono-azo laked nanoscale pigments. Suchcompositions are useful, for example, as ink compositions. Thecompositions generally include organic mono-azo laked nanoscalepigments, a polymeric dispersant, and an organic liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

Disclosed in commonly assigned U.S. patent application Ser. No.11/759,913 to Rina Carlini et al. filed Jun. 7, 2007, is a nanoscalepigment particle composition, comprising: an organic monoazo lakedpigment including at least one functional moiety, and a sterically bulkystabilizer compound including at least one functional group, wherein thefunctional moiety associates non-covalently with the functional group;and the presence of the associated stabilizer limits the extent ofparticle growth and aggregation, to afford nanoscale-sized pigmentparticles. Also disclosed is a process for preparing nanoscale-sizedmonoazo laked pigment particles, comprising: preparing a first reactionmixture comprising: (a) a diazonium salt including at least onefunctional moiety as a first precursor to the laked pigment and (b) aliquid medium containing diazotizing agents generated in situ fromnitrous acid derivatives; and preparing a second reaction mixturecomprising: (a) a coupling agent including at least one functionalmoiety as a second precursor to the laked pigment and (b) a stericallybulky stabilizer compound having one or more functional groups thatassociate non-covalently with the coupling agent; and (c) a liquidmedium combining the first reaction mixture into the second reactionmixture to form a third solution and effecting a direct couplingreaction which forms a monoazo laked pigment composition wherein thefunctional moiety associates non-covalently with the functional groupand having nanoscale particle size. Further disclosed is a process forpreparing nanoscale monoazo laked pigment particles, comprising:providing a monoazo precursor dye to the monoazo laked pigment thatincludes at least one functional moiety; subjecting the monoazoprecursor dye to an ion exchange reaction with a metal cation salt inthe presence of a sterically bulky stabilizer compound having one ormore functional groups; and precipitating the monoazo laked pigment asnanoscale particles, wherein the functional moiety of the pigmentassociates non-covalently with the functional group of the stabilizerand having nanoscale particle size.

Disclosed in commonly assigned U.S. patent application Ser. No.11/759,906 to Maria Birau et al. filed Jun. 7, 2007, is a nanoscalepigment particle composition, comprising: a quinacridone pigmentincluding at least one functional moiety, and a sterically bulkystabilizer compound including at least one functional group, wherein thefunctional moiety of the pigment associates non-covalently with thefunctional group of the stabilizer; and the presence of the associatedstabilizer limits the extent of particle growth and aggregation, toafford nanoscale-sized particles. Also disclosed is a process forpreparing nanoscale quinacridone pigment particles, comprising:preparing a first solution comprising: (a) a crude quinacridone pigmentor pigment precursor including at least one functional moiety and (b) aliquid medium; preparing a second solution comprising: (a) a stericallybulky stabilizer compound having one or more functional groups thatassociate non-covalently with the pigment functional moiety, and (b) aliquid medium; combining the first solution into the second solution toform a third reaction mixture which forms a quinacridone pigmentcomposition of nanoscale particle size and wherein the functional moietyof the pigment associates non-covalently with the functional group ofthe stabilizer. Still further is disclosed a process for preparingnanoscale quinacridone pigment particles, comprising: preparing a firstsolution comprising a quinacridone pigment including at least onefunctional moiety in an acid; preparing a second solution comprising anliquid medium and a sterically bulky stabilizer compound having one ormore functional groups that associate non-covalently with the functionalmoiety of the pigment; treating the second solution with the firstsolution to precipitate quinacridone pigment of nanoscale particle size,wherein the functional moiety of the pigment associates non-covalentlywith the functional group of the stabilizer.

The entire disclosure of the above-mentioned application is totallyincorporated herein by reference.

BACKGROUND

Pigments are a class of colorants useful in a variety of applicationssuch as, for example, paints, plastics and inks. Dyes have typicallybeen the colorants of choice for inkjet printing inks because they arereadily soluble colorants which enable jetting of the ink. Dyes havealso offered superior and brilliant color quality with an expansivecolor gamut for inks, when compared with conventional pigments. However,since dyes are molecularly dissolved in the ink vehicle, they are oftensusceptible to unwanted interactions that lead to poor ink performance,for example photooxidation from light (will lead to poor lightfastness),dye diffusion from the ink into paper or other substrates (will lead topoor image quality and showthrough), and the ability for the dye toleach into another solvent that makes contact with the image (will leadto poor water/solventfastness). In certain situations, pigments are thebetter alternative as colorants for inkjet printing inks since they areinsoluble and cannot be molecularly dissolved within the ink matrix, andtherefore do not experience colorant diffusion. Pigments are alsosignificantly less expensive than dyes, and so are attractive colorantsfor use in all printing inks.

Key issues with using pigments for inkjet inks are their large particlesizes and wide particle size distribution, the combination of which canpose critical problems with reliable jetting of the ink (i.e. inkjetnozzles are easily blocked). Pigments are rarely obtained in the form ofsingle crystal particles, but rather as large aggregates of crystals andwith wide distribution of aggregate sizes. The color characteristics ofthe pigment aggregate can vary widely depending on the aggregate sizeand crystal morphology. Thus, there is a need addressed by embodimentsof the present invention, for smaller pigment particles that minimize oravoid the problems associated with conventional pigment particles. Thepresent nanosized pigment particles are useful in for example paints,coatings and inks (e.g., inkjet printing inks) and other compositionswhere pigments can be used such as plastics, optoelectronic imagingcomponents, photographic components and cosmetics.

A printing ink is generally formulated according to strict performancerequirements demanded by the intended market application and requiredproperties. Whether formulated for office printing or for productionprinting, a particular ink is expected to produce images that are robustand durable under stress conditions. In a typical design of apiezoelectric ink jet printing device, the image is applied by jettingappropriately colored inks during four to six rotations (incrementalmovements) of a substrate (an image receiving member or intermediatetransfer member) with respect to the ink jetting head, i.e., there is asmall translation of the printhead with respect to the substrate inbetween each rotation. This approach simplifies the printhead design,and the small movements ensure good droplet registration. At the jetoperating temperature, droplets of liquid ink are ejected from theprinting device and, when the ink droplets contact the surface of therecording substrate, either directly or via an intermediate heatedtransfer belt or drum, they quickly solidify to form a predeterminedpattern of solidified ink drops.

The following documents provide background information:

Hideki Maeta et al., “New Synthetic Method of Organic Pigment NanoParticle by Micro Reactor System,” in an abstract available on URLaddress:http://aiche.confex.com/aiche/s06/preliminaryprogram/abstract_(—)40072.htm,which describes a new synthetic method of an organic pigment nanoparticle was realized by micro reactor. A flowing solution of an organicpigment, which dissolved in an alkaline aqueous organic solvent, mixedwith a precipitation medium in a micro channel. Two types of microreactor can be applied efficiently on this build-up procedure withoutblockage of the channel. The clear dispersion was extremely stable andhad narrow size distribution, which were the features, difficult torealize by the conventional pulverizing method (breakdown procedure).These results proved the effectiveness of this process on micro reactorsystem.

U.S. Patent Application Publication No. 2005/0109240 describes a methodof producing a fine particle of an organic pigment, containing the stepsof: flowing a solution of an organic pigment dissolved in an alkaline oracidic aqueous medium, through a channel which provides a laminar flow;and changing a pH of the solution in the course of the laminar flow.

WO 2006/132443 A1 describes a method of producing organic pigment fineparticles by allowing two or more solutions, at least one of which is anorganic pigment solution in which an organic pigment is dissolved, toflow through a microchannel, the organic pigment solution flows throughthe microchannel in a non-laminar state. Accordingly, the contact areaof solutions per unit time can be increased and the length of diffusionmixing can be shortened, and thus instantaneous mixing of solutionsbecomes possible. As a result, nanometer-scale monodisperse organicpigment fine particles can be produced in a stable manner.

K. Balakrishnan et al., “Effect of Side-Chain Substituents onSelf-Assembly of Perylene Diimide Molecules: Morphology Control,” J. Am.Chem. Soc., vol. 128, p. 7390-98 (2006) describes the use ofcovalently-linked aliphatic side-chain substituents that werefunctionalized onto perylene diimide molecules so as to modulate theself-assembly of molecules and generate distinct nanoparticlemorphologies (nano-belts to nano-spheres), which in turn impacted theelectronic properties of the material. The side-chain substituentsstudied were linear dodecyl chain, and a long branched nonyldecyl chain,the latter substituent leading to the more compact, sphericalnanoparticle.

WO 2006/011467 discloses a pigment, which is used, for example, in colorimage display devices and can form a blue pixel capable of providing ahigh level of bright saturation, particularly a refined pigment, whichhas bright hue and is excellent in pigment properties such aslightfastness, solvent resistance and heat resistance, and a process forproducing the same, a pigment dispersion using the pigment, and an inkfor a color filter. The pigment is a subphthalocyanine pigment that isprepared by converting subphthalocyanine of the specified formula, to apigment, has diffraction peaks at least at diffraction angles (2θ) 7.0°,12.3°, 20.4° and 23.4° in X-ray diffraction and an average particlediameter of 120 to 20 nm.

U.S. Patent Application Publication No. 2006/0063873 discloses a processfor preparing nano water paint comprising the steps of: A. modifying thechemical property on the surface of nano particles by hydroxylation forforming hydroxyl groups at high density on the surface of the nanoparticles; B. forming self-assembly monolayers of low surface energycompounds on the nano particles by substituting the self-assemblymonolayers for the hydroxyl groups on the nano particles fordisintegrating the clusters of nano particles and for forming theself-assembly monolayers homogeneously on the surface of the nanoparticles; and C. blending or mixing the nano particles havingself-assembly monolayers formed thereon with organic paint to form nanowater paint.

WO 2006/024103 discloses nanopigments prepared from organic IR dye andNa-bentonite with CEC of 95 mmole Na per 100 g of bentonite, at roomtemperature, by dissolving the Na-bentonite in water and mixing for 2hours, and mixing in the dye, dissolved in ethanol, for 18 hours. Theprecipitate is filtered, washed three times with water/ethanol mixture,dried at 105° C. for 10 hours, and milled in a kitchen miller for 2mins. 0.3 parts of the nanopigments were mixed to 100 parts ofpulverized SPG resin and processed in an extruder with a die temperatureof 190° C. to form transparent, faintly green or grey colored extrudateswhich were used to press film of 0.4 mm thickness at 160° C. The filmswere used to prepare IR-active laminated glass. Near infrared absorptionspectra of the glass structures were obtained in a Perkin-ElmerSpectrophotometer.

WO 2006/005521 discloses a photoprotective composition comprising, in aphysiologically acceptable medium: a) at least one aqueous phase, b) atleast hydrophilic metal oxide nanoparticles, c) at least onevinylpyrrolidone homopolymer. The reference also discloses the use of atleast one vinylpyrrolidone homopolymer in a photoprotective compositioncomprising at least one aqueous phase and at least hydrophilic metaloxide nanoparticles for the purpose of reducing the whitening and/or ofimproving the stability of the said composition.(dispersibility of thenanoparticles in the aqueous phase).

WO 2006/005536 discloses a method for producing nanoparticles, inparticular, pigment particles. Said method consists of the followingsteps: (i) a raw substance is passed into the gas phase, (ii) particlesare produced by cooling or reacting the gaseous raw substance and (iii)an electrical charge is applied to the particles during the productionof the particles in step (ii), in a device for producing nanoparticles.The disclosure further relates to a device for producing nanoparticles,comprising a supply line, which is used to transport the gas flow intothe device, a particle producing and charging area in order to produceand charge nanoparticles at essentially the same time, and an evacuationline which is used to transport the charged nanoparticles from theparticle producing and charging area.

Japanese Patent Application Publication No. JP 2005238342 A2 disclosesirradiating ultrashort pulsed laser to organic bulk crystals dispersedin poor solvents to induce ablation by nonlinear absorption for crushingthe crystals and recovering the resulting dispersions of scatteredparticles. The particles with average size approximately 10 nm areobtained without dispersants or grinding agents for contaminationprevention and are suitable for pigments, pharmaceuticals, etc.

U.S. Patent Application Publication No. 2003/0199608 discloses afunctional material comprising fine coloring particles having an averageprimary particle diameter of 1 to 50 nm in a dried state, and having aBET specific surface area value of 30 to 500 m.sup.2/g and a lighttransmittance of not less than 80%. The functional material composed offine coloring particles, exhibits not only an excellent transparency butalso a high tinting strength and a clear hue.

U.S. Pat. No. 6,837,918 discloses a process and apparatus that collectspigment nanoparticles by forming a vapor of a pigment that is solid atroom temperature, the vapor of the pigment being provided in an inertgaseous carrying medium. At least some of the pigment is solidifiedwithin the gaseous stream. The gaseous stream and pigment material ismoved in a gaseous carrying environment into or through a dry mechanicalpumping system. While the particles are within the dry mechanicalpumping system or after the nanoparticles have moved through the drypumping system, the pigment material and nanoparticles are contactedwith an inert liquid collecting medium.

U.S. Pat. No. 6,537,364 discloses a process for the fine division ofpigments which comprises dissolving coarsely crystalline crude pigmentsin a solvent and precipitating them with a liquid precipitation mediumby spraying the pigment solution and the precipitation medium throughnozzles to a point of conjoint collision in a reactor chamber enclosedby a housing in a microjet reactor, a gas or an evaporating liquid beingpassed into the reactor chamber through an opening in the housing forthe purpose of maintaining a gas atmosphere in the reactor chamber, andthe resulting pigment suspension and the gas or the evaporated liquidbeing removed from the reactor through a further opening in the housingby means of overpressure on the gas entry side or underpressure on theproduct and gas exit side.

U.S. Pat. No. 5,679,138 discloses a process for making ink jet inks,comprising the steps of: (A) providing an organic pigment dispersioncontaining a pigment, a carrier for the pigment and a dispersant; (B)mixing the pigment dispersion with rigid milling media having an averageparticle size less than 100 μm; (C) introducing the mixture of step (B)into a high speed mill; (D) milling the mixture from step (C) until apigment particle size distribution is obtained wherein 90% by weight ofthe pigment particles have a size less than 100 nanometers (nm); (E)separating the milling media from the mixture milled in step (D); and(F) diluting the mixture from step (E) to obtain an ink jet ink having apigment concentration suitable for ink jet printers.

Japanese Patent Application Publications Nos. JP 2007023168 and JP2007023169 discloses providing a pigment dispersion compound excellentin dispersibility and flowability used for the color filter which hashigh contrast and weatherability. The solution of the organic material,for example, the organic pigment, dissolved in a good solvent under theexistence of alkali soluble binder (A) which has an acidic group, and apoor solvent which makes the phase change to the solvent are mixed. Thepigment nanoparticles dispersed compound re-decentralized in the organicsolvent containing the alkali soluble binder (B) which concentrates theorganic pigment nanoparticles which formed the organic pigment as theparticles of particle size less than 1 μm, and further has the acidicgroup.

Kazuyuki Hayashi et al., “Uniformed nano-downsizing of organic pigmentsthrough core-shell structuring,” Journal of Materials Chemistry, 17(6),527-530 (2007) discloses that mechanical dry milling of organic pigmentsin the presence of mono-dispersed silica nanoparticles gave core-shellhybrid pigments with uniform size and shape reflecting those of theinorganic particles, in striking contrast to conventional milling as abreakdown process, which results in limited size reduction and wide sizedistribution.

U.S. Patent Application Publication No. 2007/0012221 describes a methodof producing an organic pigment dispersion liquid, which has the stepsof: providing an alkaline or acidic solution with an organic pigmentdissolved therein and an aqueous medium, wherein a polymerizablecompound is contained in at least one of the organic pigment solutionand the aqueous medium; mixing the organic pigment solution and theaqueous medium; and thereby forming the pigment as fine particles; thenpolymerizing the polymerizable compound to form a polymer immobile fromthe pigment fine particles.

The appropriate components and process aspects of each of the foregoingmay be selected for the present disclosure in embodiments thereof, andthe entire disclosure of the above-mentioned references are totallyincorporated herein by reference.

SUMMARY

The present disclosure addresses these and other needs, by providingnanoscale pigment particle compositions, and non-aqueous compositionscomprising such nanoscale pigment particle compositions.

In an embodiment, the present disclosure provides a nanoscale pigmentparticle composition, comprising:

an organic monoazo laked pigment including at least one functionalmoiety, and

a sterically bulky stabilizer compound including at least one functionalgroup,

wherein the functional moiety of the pigment associates non-covalentlywith the functional group of the stabilizer; and

the presence of the associated stabilizer limits the extent of particlegrowth and aggregation, to afford nanoscale-sized pigment particles.

In another embodiment, the disclosure provides ink compositions, such asnon-aqueous ink compositions, generally comprising at least a carriersuch as an organic liquid, a polymeric dispersant, and the abovenanoscale pigment particle composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a two-dimensional b* a* Gamut for pigmented coatingsaccording to embodiments.

FIG. 2 shows a relationship between hue angle and normalized lightscatter index (NLSI) for pigmented coatings prepared according toembodiments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of the present disclosure provide non-aqueous compositionscontaining nanoscale pigment particle compositions. The non-aqueouscompositions generally comprise a polymeric dispersant, an organicliquid, and nanoscale pigment particle compositions comprising anorganic monoazo laked pigment including at least one functional moietythat associates non-covalently with a functional group from a stericallybulky stabilizer compound. The presence of the associated stabilizerlimits the extent of particle growth and aggregation, to affordnanoscale particles. The non-aqueous compositions are useful, forexample, as ink compositions.

Organic monoazo “laked” pigments are the insoluble metal salt colorantsof monoazo colorants which can include monoazo dyes or pigments, and incertain geographic regions these pigments have been referred to aseither “toners” or “lakes”. The process of ion complexation with a metalsalt, or “laking” process, provides decreased solubility of thenon-ionic monoazo pigment, which can enhance the migration resistanceand thermal stability properties of a monoazo pigment, and therebyenable the applications of such pigments for robust performance, such ascolorizing plastics and heat-stable paints for outdoor use. Formula 1depicts a general representation of monoazo laked pigments, which areionic compounds that are structurally comprised of a diazo group(denoted G_(d)) and a nucleophilic coupling group (denoted as G_(c))that are linked together with one azo (N═N) functional group, and acation (M^(n+)) which is typically a metal salt. Either or both of thegroups G_(d) and G_(c) can contain one or more ionic functional moieties(denoted as FM), such as sulfonate or carboxylate anions or the like.

As an example, the organic monoazo laked pigment PR 57:1 (“PR” refers toPigment Red) has two functional moieties of two different types, asulfonate anion group (SO₃ ⁻) and carboxylate anion group (CO₂ ⁻) and ametal counter-cation M⁺ that is chosen from Group 2 alkaline earthmetals such as Ca²⁺. Other monoazo laked pigment compositions also existthat have a counter-cation chosen from either Group 2 alkaline earthmetals (Be, Mg, Ca, Sr, Ba,), Group 3 metals (B, Al, Ga), Group 1 alkalimetals(Li, Na, K, Cs), the transition metals such as Cr, Mn, Fe, Ni, Cu,Zn, or others non-metallic cations such as ammonium (NR₄ ⁺), phosphonium(PR₄ ⁺) wherein R-group can be H or alkyl group having from about 1 toabout 12 carbons. Further, the azo group in the compounds can generallyassume one or more tautomeric forms, such as the “azo” tautomer formwhich has the (N═N) linkage, and the “hydrazone” tautomer form which hasthe (C═N—NH—) linkage that is stabilized by an intramolecular hydrogenbond, where the hydrazone tautomer is known to be the preferredstructural form for PR 57:1.

It is understood that formula (1) is understood to denote both suchtautomer forms. Due to the structural nature of monoazo laked pigmentsbeing ionic salts, it is possible to have compounds that associatenon-covalently with the pigment, such as organic or inorganic ioniccompounds that can associate directly through ionic or coordination-typebonding, and typically with the counter-cation group like M^(n+). Suchionic compounds are included in a group of compounds which herein arereferred to as “stabilizers”, and that function to reduce the surfacetension of the pigment particle and neutralize attractive forces betweentwo or more pigment particles or structures, thereby stabilizing thechemical and physical structure of the pigment.

The term “complementary” as used in “complementary functional moiety” ofthe stabilizer indicates that the complementary functional moiety iscapable of noncovalent chemical bonding with the functional moiety ofthe organic pigment and/or the functional moiety of a pigment precursor.

The term “precursor” as used in “precursor to the organic pigment” canbe any chemical substance that is an advanced intermediate in the totalsynthesis of a compound (such as the organic pigment). In embodiments,the organic pigment and the precursor to the organic pigment may or maynot have the same functional moiety. In embodiments, the precursor tothe organic pigment may or may not be a colored compound. In still otherembodiments, the precursor and the organic pigment can have differentfunctional moieties. In embodiments, where the organic pigment and theprecursor have a structural feature or characteristic in common, thephrase “organic pigment/pigment precursor” is used for conveniencerather than repeating the same discussion for each of the organicpigment and the pigment precursor.

The functional moiety (denoted as FM) of the organic pigment/precursorcan be any suitable moiety capable of non-covalent bonding with thecomplementary functional group of the stabilizer. Illustrativefunctional moieties of the organic pigment/precursor include (but arenot limited to) the following: sulfonate/sulfonic acid,(thio)carboxylate/(thio)carboxylic acid, phosphonate/phosphonic acid,ammonium and substituted ammonium salts, phosphonium and substitutedphosphonium salts, substituted carbonium salts, substituted aryliumsalts, alkyl/aryl (thio)carboxylate esters, thiol esters, primary orsecondary amides, primary or secondary amines, hydroxyl, ketone,aldehyde, oxime, hydroxylamino, enamines (or Schiff base), porphyrins,(phthalo)cyanines, urethane or carbamate, substituted ureas, guanidinesand guanidinium salts, pyridine and pyridinium salts, imidazolium and(benz)imidazolium salts, (benz)imidazolones, pyrrolo, pyrimidine andpyrimidinium salts, pyridinone, piperidine and piperidinium salts,piperazine and piperazinium salts, triazolo, tetraazolo, oxazole,oxazolines and oxazolinium salts, indoles, indenones, and the like.

Pigment precursors for making monoazo laked nanopigments consist of asubstituted aniline precursor (denoted as “DC” in Table 1) which formsthe diazo group G_(d) of Formula (1), a nucleophilic or basic couplingcompound (denoted as “CC” in Tables 2-6) which leads to the couplinggroup G_(c) of Formula (1), and a cation salt which is preferably ametal (denoted as “M” as shown in Formula (1)). Representative examplesof the aniline precursor of laked monoazo pigments that have thefunctional moiety capable of non-covalent bonding with a complementaryfunctional group on the stabilizer, include (but are not limited to) thefollowing structures (with the functional moiety “FM” denoted, ifapplicable).

In an embodiment, the substituted aniline precursor (DC) which leads tothe diazonium group can be of the formula (2):

where R₁, R₂, and R₃ independently represent H, a straight or branchedalkyl group of from about 1 to about 10 carbon atoms (such as methyl,ethyl, propyl, butyl, and the like), halogen (such as Cl, Br, I), NH₂,NO₂, CO₂H, CH₂CH₃, and the like; and functional moiety FM representsSO₃H, —C(═O)—NH-Aryl-SO₃ ⁻ where the aryl group can be unsubstituted orsubstituted with either halogens (such as Cl, Br, I, F) or alkyl groupshaving from about 1 to about 10 carbons (such as methyl, ethyl, propyl,butyl and the like) CO₂H, halogen (such as Cl, Br, I), NH₂, —C(═O)—NH₂,and the like. The substituted aniline precursor (DC) can be also beTobias Acid, of the formula (3):

Specific examples of types of aniline precursors (DC) that are used tomake the diazo group G_(d) in the monoazo laked pigments include thoseof Table 1:

TABLE 1

Precursor Functional to Moiety Group G_(d) FM R₁ R₂ R₃ DC1 SO₃H CH₃ HNH₂ DC2 SO₃H CH₃ Cl NH₂ DC3 SO₃H Cl CH₃ NH₂ DC4 SO₃H Cl CO₂H NH₂ DC5SO₃H Cl CH₂CH₃ NH₂ DC6 SO₃H Cl Cl NH₂ DC7 SO₃H H NH₂ H DC8 SO₃H H NH₂CH₃ DC9 SO₃H NH₂ H Cl DC10 SO₃H H H NH₂ DC11 SO₃H H NH₂ H DC12 SO₃H NO₂NH₂ H DC13

NH₂ CH₃ H DC14 CO₂H H H NH₂ DC15 Cl H H NH₂ DC16 NH₂ CH₃ H H DC17 NH₂ HCH₃ H DC18

NH₂ CH₃ H DC19

H NH₂ H DC20 NH₂ H H H DC21

In an embodiment, the coupling group G_(c) of Formula (1) can includeβ-naphthol and derivatives of Formula (4), naphthalene sulfonic acidderivatives of Formulas (5) and (6), pyrazolone derivatives of Formula(7), acetoacetic arylide derivatives of Formula (8), and the like. Informulas (4)-(8), the asterisk “*” denotes the point of coupling orattachment to the monoazo (N═N) linkage.

where FM represents H, CO₂H, SO₃H, —C(═O)—NH-Aryl-SO₃ ³¹ where the arylgroup can be unsubstituted or substituted with either halogens (such asCl, Br, I, F) or alkyl groups having from about 1 to about 10 carbons(such as methyl, ethyl, propyl, butyl and the like) CO₂H, halogen (suchas Cl, Br, I), NH₂, —C(═O)—NH₂, substituted benzamides such as:

wherein groups R₂′ R₃′, R₄′ and R₅′ can independently be H, alkyl groupshaving from about 1 to 10 carbons (such as methyl, ethyl, propyl, butyl,and the like), alkoxyl groups (such as OCH₃, OCH₂CH₃, and the like),hydroxyl or halogen (such as Cl, Br, I, F) or nitro NO₂; orbenzimidazolone amides such as:

and the like.

where FM represents preferably SO₃H, but also can represent CO₂H,—C(═O)—NH-Aryl-SO₃ ⁻ where the aryl group can be unsubstituted orsubstituted with either halogens (such as Cl, Br, I, F) or alkyl groupshaving from about 1 to about 10 carbons (such as methyl, ethyl, propyl,butyl and the like) CO₂H, halogen (such as Cl, Br, I), NH₂, —C(═O)—NH₂groups R₃ and R₄ independently represent H, SO₃H, and the like.

where FM represents preferably SO₃H, but also can represent CO₂H,—C(═O)—NH-Aryl-SO₃ ⁻ where the aryl group can be unsubstituted orsubstituted with either halogens (such as Cl, Br, I, F) or alkyl groupshaving from about 1 to about 10 carbons (such as methyl, ethyl, propyl,butyl and the like) CO₂H, halogen (such as Cl, Br, I), NH₂, —C(═O)—NH₂;R₁, R₂, R₃ and R₄ independently represent H, SO₃H, —C(═O)—NH-Phenyl, andthe like.

where G represents CO₂H, straight or branched alkyl such as having from1 to about 10 carbons atoms (such as methyl, ethyl, propyl, butyl, orthe like), and the like; and R₁′, R₂′, R₃′ and R₄′ independentlyrepresent H, halogen (such as Cl, Br, I), SO₃H, nitro (NO₂) or alkoxylgroup such as OCH₃ or OCH₂CH₃ and the like.

where R₁′ represents a straight or branched alkyl group having, forexample, from 1 to about 10 carbon atoms (such as methyl, ethyl, propyl,butyl, and the like); R₂′ represents a benzimidazolone group:

or a substituted aryl group

where each of R_(a), R_(b), and R_(c) independently represent H, astraight or branched alkyl group having, for example, from 1 to about 10carbon atoms (such as methyl, ethyl, proply, butyl, and the like),alkoxyl groups such as OCH₃ or OCH₂CH₃ and the like, halogen (such asCl, Br, I), nitro NO₂, and the like.

Representative examples of the nucleophilic coupling component as aprecursor of laked monoazo pigments which have the functional moietythat is capable of non-covalent bonding with a complementary functionalgroup on the stabilizer, include (but are not limited to) the followingstructures shown in Tables 2-6 (with the functional moiety “FM” denoted,if applicable):

TABLE 2

Precursor Class of Functional to Coupling Moiety group G_(c) ComponentFM CC1 β-Naphthol H CC2 β-oxynaphthoic acid CO₂H (“BONA”) CC3 NaphtholAS derivatives

CC6 Benzimidazolone

* = point of coupling to diazo component

TABLE 3

Precursor Class of to Coupling group G_(c) Component FM R₃ R₄ CC4aNaphthalene Sulfonic SO₃H H H Acid derivatives CC4b Naphthalene SulfonicSO₃H SO₃H H Acid derivatives * = point of coupling to diazo component

TABLE 4

Precursor Class of to Coupling group G_(c) Component FM R₁ R₂ R₃ R₄ CC5Naphthalene Sulfonic Acid derivatives SO₃H

H H SO₃H * = point of coupling to diazo component

TABLE 5

Precursor Class of to Coupling group G_(c) Component G R₁′ R₂′ R₃′ R₄′CC7 Pyrazolone deriv. CO₂H H H SO₃H H CC8 Pyrazolone deriv. CH₃ H H SO₃HH CC9 Pyrazolone deriv. CH₃ H SO₃H H H CC10 Pyrazolone deriv. CH₃ Cl HSO₃H Cl * = point of coupling to diazo component

TABLE 6

Precursor Class of to Coupling group G_(c) Component R₁′ R₂′ R_(a) R_(b)R_(c) CC11 Acetoacetic arylide CH₃

H H H CC12 Acetoacetic arylide CH₃

CH₃ H H CC13 Acetoacetic arylide CH₃

Cl H H CC14 Acetoacetic arylide CH₃

H OCH₃ H CC15 Acetoacetic benzimidazolone CH₃

— — — * = point of coupling to diazo component

The organic pigment, and in some embodiments, the organic pigmentprecursor, also generally includes a counterion as part of the overallstructure. Such counterions can be, for example, any suitable counterionincluding those that are well known in the art. Such counterions can be,for example, cations or anions of either metals or non-metals thatinclude N, P, S and the like, or carbon-based cations or anions.Examples of suitable cations include ions of Ba, Ca, Cu, Mg, Sr, Li, Na,K, Cs, Mn, Cu, Cr, Fe, Ti, Ni, Co, Zn, V, B, Al, Ga, and other metalions, as well as ammonium and phosphonium cations, mono-, di-, tri-, andtetra-substituted ammonium and phosphonium cations, where thesubstituents can be aliphatic alkyl groups, such as methyl, ethyl,butyl, stearyl and the like, as well as aryl groups such as phenyl orbenzyl and the like.

Representative examples of monoazo laked pigments comprised from aselection of substituted aniline precursors (denoted DC) which can alsoinclude Tobias Acid, nucleophilic coupling component (denoted as CC) andmetal salts (denoted as M) to provide the counter-cation M^(n+) offormula (1) are listed in Table 7, and other laked pigment structuresmay arise from other combinations of DC and CC and metal cation salt (M)that are not shown in Table 7.

TABLE 7

Color Index # Color Index G_(d) G_(c) Metal Salt (C.I.) (C.I.) NameLaked Pigment Class precursor precursor M 15500:1 Red 50:1 β-NaphtholLakes DC14 CC1 ½ Ba 15510:1 Orange 17 β-Naphthol Lakes DC7 CC1 Ba15510:2 Orange 17:1 β-Naphthol Lakes DC7 CC1 ⅔ Al 15525 Red 68β-Naphthol Lakes DC4 CC1 2 Ca 15580 Red 51 β-Naphthol Lakes DC8 CC1 Ba15585 Red 53 β-Naphthol Lakes DC3 CC1 2 Na 15585:1 Red 53:1 β-NaphtholLakes DC3 CC1 Ba 15585:3 Red 53:3 β-Naphthol Lakes DC3 CC1 Sr 15602Orange 46 β-Naphthol Lakes DC5 CC1 Ba 15630 Red 49 β-Naphthol Lakes DC21CC1 2 Na 15630:1 Red 49:1 β-Naphthol Lakes DC21 CC1 Ba 15630:2 Red 49:2β-Naphthol Lakes DC21 CC1 Ca 15630:3 Red 49:3 β-Naphthol Lakes DC21 CC1Sr 15800 Red 64 β-oxynaphthoic acid (BONA) Lakes DC20 CC2 ½ Ba 15800:1Red 64:1 β-oxynaphthoic acid (BONA) Lakes DC20 CC2 ½ Ca 15800:2 Brown 5β-oxynaphthoic acid (BONA) Lakes DC20 CC2 ½ Cu 15825:2 Red 58:2β-oxynaphthoic acid (BONA) Lakes DC9 CC2 Ca 15825:4 Red 58:4β-oxynaphthaic acid (BONA) Lakes DC9 CC2 Mn 15850:1 Red 57:1β-oxynaphthoic acid (BONA) Lakes DC1 CC2 Ca 15860:1 Red 52:1β-oxynaphthoic acid (BONA) Lakes DC3 CC2 Ca 15860:2 Red 52:2β-oxynaphthoic acid (BONA) Lakes DC3 CC2 Mn 15865:1 Red 48:1β-oxynaphthoic acid (BONA) Lakes DC2 CC2 Ba 15865:2 Red 48:2β-oxynaphthoic acid (BONA) Lakes DC2 CC2 Ca 15865:3 Red 48:3β-oxynaphthoic acid (BONA) Lakes DC2 CC2 Sr 15865:4 Red 48:4β-oxynaphthoic acid (BONA) Lakes DC2 CC2 Mn 15865:5 Red 48:5β-oxynaphthoic acid (BONA) Lakes DC2 CC2 Mg 15867 Red 200 β-oxynaphthoicacid (BONA) Lakes DC5 CC2 Ca 15880:1 Red 63:1 β-oxynaphthoic acid (BONA)Lakes DC21 CC2 Ca 15880:2 Red 63:2 β-oxynaphthoic acid (BONA) Lakes DC21CC2 Mn 15892 Red 151 Naphthol AS Lakes DC10 CC3 Ba (R₂′ = H, R₄′ = SO₃H)15910 Red 243 Naphthol AS Lakes DC2 CC3 ½ Ba (R₂′ = OCH₃, R₄′ = H) 15915Red 247 Naphthol AS Lakes DC13 CC3 Ca (R₂′ = H, R₄′ = OCH₃) 15985:1Yellow 104 Naphthalene Sulfonic Acid Lakes DC7 CC4a ⅔ Al 15990 Orange 19Naphthalene Sulfonic Acid Lakes DC15 CC4a ½ Ba 16105 Red 60 NaphthaleneSulfonic Acid Lakes DC14 CC4b 3/2 Ba 18000:1 Red 66 Naphthalene SulfonicAcid Lakes DC16 CC5 ½ Ba, Na

The complementary functional group of the stabilizer can be one or moreof any suitable moiety capable of non-covalent bonding with thefunctional moiety of the stabilizer. Illustrative complementaryfunctional groups on the stabilizer include the following:sulfonate/sulfonic acid, (thio)carboxylate/(thio)carboxylic acid,phosphonate/phosphonic acid, ammonium and substituted ammonium salts,phosphonium and substituted phosphonium salts, substituted carboniumsalts, substituted arylium salts, alkyl/aryl (thio)carboxylate esters,thiol esters, primary or secondary amides, primary or secondary amines,hydroxyl, ketone, aldehyde, oxime, hydroxylamino, enamines (or Schiffbase), porphyrins, (phthalo)cyanines, urethane or carbamate, substitutedureas, guanidines and guanidinium salts, pyridine and pyridinium salts,imidazolium and (benz)imidazolium salts, (benz)imidazolones, pyrrolo,pyrimidine and pyrimidinium salts, pyridinone, piperidine andpiperidinium salts, piperazine and piperazinium salts, triazolo,tetraazolo, oxazole, oxazolines and oxazolinium salts, indoles,indenones, and the like.

The stabilizer can be any compound that has the function of limiting theextent of pigment particle or molecular self-assembly so as to producepredominantly nanoscale-sized pigment particles. The stabilizer compoundshould have a hydrocarbon moiety that provides sufficient steric bulk toenable the function of the stabilizer to regulate pigment particle size.The hydrocarbon moiety in embodiments is predominantly aliphatic, but inother embodiments can also incorporate aromatic groups, and generallycontains at least 6 carbon atoms, such as at least 12 carbons or atleast 16 carbons, and not more than about 100 carbons, but the actualnumber of carbons can be outside of these ranges. The hydrocarbon moietycan be either linear, cyclic or branched, and in embodiments isdesirably branched, and may or may not contain cyclic moieties such ascycloalkyl rings or aromatic rings. The aliphatic branches are long withat least 2 carbons in each branch, such as at least 6 carbons in eachbranch, and not more than about 100 carbons.

It is understood that the term “steric bulk” is a relative term, basedon comparison with the size of the pigment or pigment precursor to whichit becomes non-covalently associated. In embodiments, the phrase “stericbulk” refers to the situation when the hydrocarbon moiety of thestabilizer compound that is coordinated to the pigment/precursorsurface, occupies a 3-dimensional spatial volume that effectivelyprevents the approach or association of other chemical entities (e.g.colorant molecules, primary pigment particles or small pigmentaggregate) toward the pigment/precursor surface. Thus, the stabilizershould have its hydrocarbon moiety large enough so that as severalstabilizer molecules become non-covalently associated with the chemicalentity (pigment or precursor), the stabilizer molecules act as surfacebarrier agents for the primary pigment particles and effectivelyencapsulates them, and thereby limits the growth of the pigmentparticles and affording only nanoparticles of the pigment. For example,for the pigment precursor Lithol Rubine and for the organic pigmentPigment Red 57:1, the following illustrative groups on a stabilizer areconsidered to have adequate “steric bulk” so as to enable the stabilizerto limit the extent of pigment self-assembly or aggregation and mainlyproduce pigment nano-sized particles:

Representative examples of stabilizer compounds that have both thefunctional group that non-covalently associates with the pigment and thesterically bulky hydrocarbon moiety, include (but are not limited to)the following compounds:

wherein m and n denotes the number of repeated methylene units, andwhere m can range between 1 and 50, and n can range between 1 and 5,however the values can also be outside these ranges.

In additional embodiments, other stabilizer compounds having differentstructures than those described previously may be used in addition tosterically bulky stabilizer compounds, to function as surface activeagents (or surfactants) that either prevent or limit the degree ofpigment particle aggregation. Representative examples of such surfaceactive agents include, but are not limited to, rosin natural productssuch as abietic acid, dehydroabietic acid, pimaric acid, rosin soaps(such as the sodium salt of the rosin acids), hydrogenated derivativesof rosins and their alkyl ester derivatives made from glycerol orpentaerythritol or other such hydrocarbon alcohols, acrylic-basedpolymers such as poly(acrylic acid), poly(methyl methacrylate),styrene-based copolymers such as poly(styrene sodio-sulfonate) andpoly(styrene)-co-poly(alkyl (meth)acrylate), copolymers of α-olefinssuch as 1-hexadecene, 1-octadecene, 1-eicosene, 1-triacontene and thelike, copolymers of 4-vinyl pyridine, vinyl imidazole, and vinylpyrrolidinone, polyester copolymers, polyamide copolymers, copolymers ofacetals and acetates, such as the copolymer poly(vinylbutyral)-co-(vinylalcohol)-co-(vinyl acetate).

The types of non-covalent chemical bonding that can occur between thefunctional moiety of the precursor/pigment and the complementaryfunctional group of the stabilizer are, for example, van der Waals'forces, ionic or coordination bonding, hydrogen bonding, and/or aromaticpi-stacking bonding. In embodiments, the non-covalent bonding ispredominately ionic bonding, but can include hydrogen bonding andaromatic pi-stacking bonding as additional or alternative types ofnon-covalent bonding between the functional moieties of the stabilizercompounds and the precursor/pigment.

The “average” pigment particle size, which is typically represented byZ-average, which is defined as an intensity mean which is derived fromthe cumulants analysis of an intensity signal obtained from dynamiclight scattering method, and also by d₅₀, which is defined as the medianparticle size value at the 50th percentile of the particle sizedistribution, wherein 50% of the particles in the distribution aregreater than the d₅₀ particle size value and the other 50% of theparticles in the distribution are less than the d₅₀ value. Averageparticle size can be measured by methods that use light scatteringtechnology to infer particle size, such as by dynamic light scattering(DLS). The term “particle diameter” as used herein refers to the lengthof the pigment particle at the longest dimension (in the case ofacicular shaped particles) as derived from images of the particlesgenerated by Transmission Electron Microscopy (TEM). The term“nano-sized”, “nanoscale”, “nanoscopic”, or “nano-sized pigmentparticles” refers to for instance, an average particle size, d₅₀, orZ-average, or an average particle diameter of less than about 150 nm,such as of about 1 nm to about 100 nm, or about 10 nm to about 80 nm.Typically, the distribution of a population of particle sizes isexpressed by a width parameter or the polydispersity index (PDI), suchas can be derived by DLS technique, and also by geometric standarddeviation (GSD) which is a dimensionless number that typically estimatesa population's dispersion of a given attribute (for instance, particlesize) about the median value of the population and is derived from theexponentiated value of the standard deviation of the log-transformedvalues. If the geometric mean (or median) of a set of numbers {A₁, A₂, .. . , A_(n)} is denoted as μ_(g), then the geometric standard deviationis calculated as:

$\sigma_{g} = {\exp\sqrt{\frac{\sum\limits_{i = 1}^{n}\left( {{\ln\; A_{i}} - {\ln\;\mu_{g}}} \right)^{2}}{n}}}$

The method of making nano-sized particles of the monoazo laked pigmentssuch as those listed in Table 7 is a process that involves at least oneor more reaction steps. A diazotization reaction is a key reaction stepfor synthesis of the monoazo laked pigment, whereby a suitable anilineprecursor (or diazo component DC, such as those listed in Table 1,Formulas (2) and (3)), is either directly or indirectly converted firstto a diazonium salt using standard procedures, such as procedures thatinclude treatment with a diazotizing agent such as nitrous acid HNO₂(for example, generated in situ by mixing sodium nitrite with dilutehydrochloric acid solution) or nitrosyl sulfuric acid (NSA), which iscommercially available or prepared by mixing sodium nitrite inconcentrated sulfuric acid. The resulting acidic mixture of diazoniumsalt is either a solution or a suspension and in embodiments is keptcold, to which can optionally be added an aqueous solution of the metalsalt (M^(n+)) that will define the specific composition of the desiredmonoazo laked pigment product, such as those listed in Table 7. Thediazonium salt solution or suspension is then transferred into asolution or suspension of a suitable coupling component (CC, such asthose listed in Tables 2-6, Formulas (4)-(8)) that can be either acidicor basic in pH and generally contain additional buffers and surfaceactive agents, including the sterically bulky stabilizer compounds suchas those described earlier, to produce a solid colorant materialsuspended as an aqueous slurry.

The solid colorant material may be the desired monoazo laked pigmentproduct, or it may be an advanced synthetic intermediate for making themonoazo laked pigment product. In the case of the latter, a two-stepprocess is required for preparing the nanosized particles of monoazolaked pigment, whereby the second step involves rendering the advancedsynthetic intermediate of the first step above (the pigment precursor)into homogeneous liquid solution by treatment with either strong acid oralkaline base, treating this solution with one or more surface activeagents in addition to sterically bulky stabilizer compounds, asdescribed earlier, followed lastly by treatment with the required metalsalt solution to provide the required laked pigment composition as asolid precipitate, said metal salt solution effectively functioning as apigment precipitating agent. Several chemical as well as physicalprocessing factors can affect the final particle size and distributionof the monoazo laked pigment, including stoichiometries of the DC and CCreactants, metal salt, surface active agents, and stabilizer compounds,concentration of chemical species in the liquid medium, pH of liquidmedium, temperature, addition rate, order of addition, agitation rate,post-reaction treatments such as heating, isolation and washing ofparticles, and drying conditions.

In embodiments is disclosed a two-step method of making nanosizedmonoazo laked red pigments, for example Pigment Red 57:1, wherein theadvanced pigment precursor Lithol Rubine is first synthesized as apotassium salt and is a water-soluble orange dye. The first stepinvolves the diazotization of 2-amino-5-methyl-benzenesulfonic acid (DC1in Table 1) by first dissolving the DC in dilute aqueous potassiumhydroxide solution (0.5 mol/L) and cooling to a temperature of about −5°C. to about 10° C., and then treating the solution with an aqueoussolution of sodium nitrite (20 wt %), following with slow addition ofconcentrated hydrochloric acid at a rate that maintains the internalreaction temperature between −5° C. and +5° C. The resulting suspensionthat forms is stirred for additional time at cool temperature, so as toensure completeness of diazotization, and then the suspension iscarefully transferred to a second solution containing3-hydroxy-2-naphthoic acid dissolved in dilute alkaline solution (0.5mol/L potassium hydroxide) using vigorous agitation as the colorantproduct is produced in the aqueous slurry. After stirring for additionaltime of at least 1 hour at room temperature, the colorant product(Lithol Rubine-potassium salt) is isolated by filtration as an orangedyestuff and washed with deionized water to remove excess acid and saltby-products.

The second step of this process involves redispersing the orange LitholRubine-potassium salt dyestuff in deionized water to a concentrationthat can range from about 0.5 wt % to about 20 wt %, such as from about1.5 wt % to about 10 wt % or from about 3.5 wt % to about 8 wt %, butthe concentrations can also be outside of these ranges. The colorantsolids in the slurry is then dissolved completely into liquid solutionby treatment with aqueous alkaline base, such as sodium hydroxide orpotassium hydroxide or ammonium hydroxide solution, until the pH levelis high, such as above pH 8.0 or above pH 9.0 or above pH 10.0. To thisalkaline solution of dissolved Lithol Rubine colorant can be optionallyadded a surface active agent as described earlier, in particularembodiments surface active agent such as rosin soaps, delivered as anaqueous solution in the amount ranging from 0.1 wt % to 20 wt % based oncolorant solids, such as in an amount ranging from 0.5 wt % to about 10wt %, or in an amount ranging from 1.0 wt % to about 8.0 wt % based oncolorant solids, but the amount used can also be outside of theseranges.

In embodiments, the preparation of ultrafine and nanosized particles ofthe monoazo laked Pigment Red 57:1 was only enabled by the additionaluse of a stabilizer compound having a functional moiety that couldnon-covalently bond to the complementary functional moiety of thepigment as well as branched aliphatic functional groups that couldprovide steric bulk to the pigment particle surface. In embodiments,particularly suitable sterically bulky stabilizer compounds are branchedhydrocarbons with either carboxylate or sulfonate functional groups,compounds such as di[2-ethylhexyl]-3-sulfosuccinate sodium or sodium2-hexyldecanoate, and the like. The stabilizer compound is introduced asa solution or suspension in a liquid that is predominantly aqueous butmay optionally contain a polar, water-miscible co-solvent such as THF,iso-propanol, NMP, Dowanol and the like, to aid dissolution of thestabilizer compound, in an amount relative to colorant moles rangingfrom about 5 mole-percent to about 100 mole-percent, such as from about20 mole-percent to about 80 mole-percent, or from about 30 mole-percentto about 70 mole-percent, but the concentrations used can also beoutside these ranges and in large excess relative to moles of colorant.

Lastly, the metal cation salt is added to transform the pigmentprecursor (Lithol Rubine-potassium salt in embodiments) into the desiredmonoazo laked pigment (Pigment Red 57:1 in embodiments) as aprecipitated pigment. The aqueous solution of metal salt (calciumchloride in embodiments) with concentration ranging anywhere from 0.1mol/L to about 2 mol/L, is slowly added dropwise in nearlystoichiometric quantities such as amounts ranging from 1.0 molarequivalents relative to about 2.0 molar equivalents, or from 1.1 toabout 1.5 molar equivalents, or from 1.2 to about 1.4 molar equivalentsrelative to moles of colorant, however the amounts used can also beoutside of these ranges and in large excess.

The type of metal salt can have an impact on the degree of formation ofnanosized pigment particles of monoazo laked pigments, in particular thetype of ligand that is coordinated to the metal cation in the rawmaterial and the relative ease with which it is displaced by a competingligand from either the pigment functional moiety or the complementaryfunctional moiety of the stabilizer compound, or both. In embodimentsfor monoazo laked Pigment Red 57:1, the nanosized particles are formedusing calcium (II) salts with ligands such as chloride, sulfate,acetate, and hydroxide; however a particularly desirable metal salt iscalcium chloride for fastest reactivity.

The rates of addition of metal salt solution can also vary. For example,the slower the rate of addition, the more controlled is the rate ofpigment crystal formation and particle aggregation, and therefore thesmaller the pigment particles become.

Also important is the agitation rate and mixing pattern as the pigmentformation/precipitation step is occurring. The higher the agitation rateand the more dynamic or complex is the mixing pattern (i.e. with bafflesto prevent dead mixing zones), the smaller is the average particlediameter and the more narrow is the particle size distribution, asobservable by Transmission Electron Microscopy (TEM) imaging.

Temperature during the pigment precipitation step using the metal saltsolution is also important. In embodiments, lower temperatures aredesired, such as from about 10° C. to about 50° C., or from about 15° C.to about 35° C., but the temperature can also be outside of theseranges.

In embodiments, the slurry of pigment nanoparticles is not treated norprocessed any further, such as additional heating, but instead isisolated by vacuum filtration through membrane filter cloth havingaverage pore size of 0.45 micron or 0.8 micron diameter. The pigmentsolids can be washed copiously with deionized water to remove excesssalts or additives that were not being non-covalently bound to thepigment particles, as intended by the stabilizer compounds. The pigmentsolids are subsequently dried by freeze-drying under high vacuum toafford high quality, non-agglomerated pigment particles that when imagedby TEM, exhibited primary pigment particles and small aggregates rangingin diameters from about 30 nm to about 150 nm, and predominantly fromabout 50 nm to about 125 nm. (Here, it is noted that average particlesize d₅₀ and particle size distributions are measured by Dynamic LightScattering, an optical measurement technique that estimates thehydrodynamic radius of non-spherical pigment particles gyrating andtranslating in a liquid dispersion via Brownian motion, by measuring theintensity of the incident light scattered from the moving particles. Assuch, the d₅₀ particle size metric obtained by DLS technique is always alarger number than the actual particle diameters observed by TEMimaging.)

Characterization of the chemical composition of washed and driednanosized pigment particles are performed by NMR spectroscopy andelemental analysis. In embodiments, the composition of the monoazo lakedpigment Red 57:1 indicated that the nanosized particles prepared by themethod described above, using di[2-ethylhexyl]-3-sulfosuccinate sodiumas the sterically bulky stabilizer, retained at least 80% of thesterically bulky stabilizer that was loaded into the process of makingthe nanoparticles, even after copious washing with deionized water toremove excess salts. Solid state ¹H-and ¹³C-NMR spectroscopic analysesindicated that the steric stabilizer compound was associatednon-covalently with the pigment as a calcium salt, and the chemicalstructure of the pigment adopted the hydrazone tautomer form, as shownin Figure below.

Pigment particles of monoazo laked pigments such as PR 57:1 that havesmaller particle sizes could also be prepared by the above two-stepmethod with the use of surface active agents alone depending on theconcentrations and process conditions employed, but the pigment productdid not predominantly exhibit nano-sized particles nor did the particlesexhibit regular morphologies. By comparison, in the absence of using thesterically bulky stabilizer compound, the two-step method describedabove typically produced rod-like particle aggregates, ranging inaverage particle diameter from 200-700 nm and with wide particledistribution, and such particles were difficult to disperse into apolymer coating matrix and gave poor coloristic properties. Inembodiments, the combined use of a suitable sterically bulky stabilizercompound, such as branched alkanesulfonates or alkylcarboxylates, with aminor amount of suitable surface active agent such as derivatives ofrosin-type natural products, by the two-step process would afford thesmallest fine pigment particles in the nanometer-scale diameters, morenarrow particle size distribution, and low aspect ratio. Variouscombinations of these compounds, in addition to variations with processparameters such as stoichiometry of reactants, concentration, additionrate, temperature, agitation rate, reaction time, and post-reactionproduct recovery processes, enables the formation of pigment particleswith tunable average particle size (d₅₀) from nanoscale sizes (about 1to about 100 nm) to mesoscale sizes (about 100 to about 500 nm) orlarger. The dispersion ability and coloristic properties (L*, a*, b*,chroma, hue angle, light scatter index) of the pigment particles in athin polymer binder coating were directly correlated to the averagepigment particle size, which in turn was impacted by the structural typeand amount of sterically bulky stabilizer compound that was employed inthe synthesis process.

The advantages of this process include the ability to tune particle sizeand composition for the intended end use application of the monoazolaked pigment, such as toners and inks and coatings, which includephase-change, gel-based and radiation-curable inks, solid and non-polarliquid inks, solvent-based inks and aqueous inks and ink dispersions.For the end-use application in piezoelectric inkjet printing, nanosizedparticles are advantageous to ensure reliable inkjet printing andprevent blockage of jets due to pigment particle agglomeration. Inaddition, nanosized pigment particles are advantageous for offeringenhanced color properties in printed images, since in embodiments thecolor properties of nanosized particles of monoazo laked pigment Red57:1 were tunable with particle size, whereby as average particle sizewas decreased to nanometer-scale, the hue angles were shifted fromyellowish-red hues to bluish-red hues by an amount ranging from about 5to about 35° in the color gamut space.

The method of making nanosized particles of monoazo laked pigments canalso be performed by a one-step method, wherein a suitable anilineprecursor (or diazo component DC, such as those listed in Table 1), iseither directly or indirectly converted first to a diazonium salt usingstandard procedures, such as that include treatment with a diazotizingagent such as nitrous acid HNO₂ (for example, generated in situ bymixing sodium nitrite with dilute hydrochloric acid solution) ornitrosyl sulfuric acid (NSA), which is commercially available orprepared by mixing sodium nitrite in concentrated sulfuric acid. Theresulting acidic mixture of diazonium salt is either a solution or asuspension and is preferably kept cold, to which is added an aqueoussolution of the metal salt (M^(n+)) that will define the specificcomposition of the desired monoazo laked pigment product, such as thoselisted in Table 7. The diazonium salt solution or suspension is thentransferred into a solution or suspension of a suitable couplingcomponent (CC, such as those listed in Tables 2-6) that can be eitheracidic or basic in pH and contain additional buffers and surface activeagents, including the sterically bulky stabilizer compounds such asthose described earlier, to produce a solid colorant material suspendedas an aqueous slurry. The solid colorant material produced is thedesired monoazo laked pigment product suspended in aqueous slurry, whichis isolated by vacuum filtration, washed with copious amounts ofdeionized water to remove excess salt by-products, and preferablyfreeze-dried under vacuum, affording fine and nanosized particles of thepigment.

In embodiments, the nanosized pigment particles that were obtained formonoazo laked pigments can range in average particle size, d₅₀, oraverage particle diameter, from about 10 nm to about 250 nm, such asfrom about 25 nm to about 175 nm, or from about 50 nm to about 150 nm,as measured by either dynamic light scattering method or from TEMimages. In embodiments, the particle size distributions can range suchthat the geometric standard deviation can range from about 1.1 to about1.9, or from about 1.2 to about 1.7, as measured by dynamic lightscattering method. The shape of the nanosized pigment particles can beone or more of several morphologies, including rods, platelets, needles,prisms or nearly spherical, and the aspect ratio of the nanosize pigmentparticles can range from 1:1 to about 10:1, such as having aspect ratiobetween 1:1 and 5:1; however the actual metric can lie outside of theseranges.

The color of the nanosized pigment particles have the same general hueas is found with larger pigment particles. However, in embodiments, isdisclosed coloristic properties of thin coatings of the nanosizedpigment particles of red monoazo laked pigments dispersed in a colorlesstransparent polymer binder (such as of poly(vinyl butyral-co-vinylalcohol-co-vinyl acetate)), that exhibited a significant shift to lowerhue angle and lower b* values that revealed more bluish magenta hues,and having either no change or a small enhancement of a* value. Inembodiments, the hue angles of the coatings dispersed with the nanosizedparticles of monoazo laked pigment such as Pigment Red 57:1 measured inthe range from about 345° to about 5° on the 2-dimensional b* a* colorgamut space, as compared with hue angles ranging from about 0° to about20° for similarly prepared polymer coatings dispersed with larger sizedparticles of Pigment Red 57:1. In embodiments is disclosed thecoloristic properties (hue angle, a*, b*, and NLSI as measure ofspecular reflectivity) of nanosized pigment particles, particularly ofmonoazo laked red pigment, that are directly correlated and tunable withthe average pigment particle size, measured by either Dynamic LightScattering or electron microscopy imaging techniques, as well as pigmentcomposition with the non-covalently associated stabilizer, the latterwhich enables the control of particle size during pigment synthesis, andalso enables enhanced dispersability within certain polymer binders forcoating or other applications.

Additionally, the specular reflectivity of the coatings of the nanosizemonoazo lakes red pigment was significantly enhanced from coatingsproduced with larger sized pigment particles, which is an indicator ofhaving very small particles being well-dispersed within the coating.Specular reflectivity was quantified as the degree of light scatteringfor the pigmented coating, a property that is dependent on the size andshape distributions of the pigment particles and their relativedispersability within the coating binder. The Normalized Light ScatterIndex (NLSI) was quantified by measuring the spectral absorbance of thecoating in a region where there is no absorbance from the chromogen ofthe monoazo laked pigment, but only absorbance due to light scatteredfrom large aggregates and/or agglomerated pigment particles dispersed inthe coating binder. The light scattering absorbance data is thennormalized to a lambda-max optical density of 1.5, resulting in the NLSIvalue, in order to directly compare the light scattering indices ofseveral pigmented coatings. The lower is the NLSI value, the smaller isthe pigment particle size within the dispersed coating matrix. Inembodiments, the NLSI value of the nanosized monoazo laked red pigmentscan range from about 0.1 to about 3.0, such as from about 0.1 to about1.0, as compared to the NLSI values observed with similarly preparedcoatings containing larger sized monoazo laked red pigments that rangeanywhere from about 3.0 to about 75 (the latter indicating a very poorlydispersed coating).

The formed nanoscale pigment particle compositions can be used, forexample, as coloring agents in a variety of compositions, such as inliquid non-aqueous ink vehicles, including inks used in conventionalpens, markers, and the like, liquid ink jet ink compositions, solid orphase change ink compositions, and the like. For example, the colorednanoparticles can be formulated into a variety of ink vehicles,including “low energy” solid inks with melt temperatures of about 60 toabout 130° C., and solvent-based liquid inks or radiation-curable suchas UV-curable liquid inks comprised of alkyloxylated monomers. Varioustypes of such compositions will now be described in more detail.

In embodiments, these nanoscale-sized pigments can be dispersed in avariety of media where such high specular reflectance is afforded.Polymeric binders (polymeric dispersants) that aid in the dispersion andcoating ability of nanoscale-sized pigments include, but are not limitedto, derivatives of rosin natural products, acrylic-based polymers,styrene-based copolymers, copolymers of α-olefins such as 1-hexadecene,1-octadecene, 1-eicosene, 1-triacontene and the like, copolymers ofvinyl pyridine, vinyl imidazole, vinyl pyrrolidinone, polyestercopolymers, polyamide copolymers, and copolymers of acetals. Otherexamples of polymeric dispersants include, but are not limited to,poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), poly(vinylacetate), poly(acrylic acid), poly(methacrylic acid), poly(vinylalcohol), poly(N-vinylcarbazole), poly(methyl methacrylate),polyvinylidene difluoride, polyesters such as MOR-ESTER 49000®,polycarbonate polymers such as Lexan®, and Merlon® M-39, andpoly(2-hydroxyethyl methacrylate), poly(styrene-b-4-vinylpyridine),polyurethane resins, polyetheretherketones, phenol-formaldehyde resins,polyols such as Pluronic® and Pluronic® R polymers, glycolic polymerssuch as polyethylene glycol polymers and their derivatives,polysulfones, polyarylethers, polyarylsulfones, and the like. Suitablemixtures of at least two polymers can also be used to dispersenanoscale-sized pigments in liquid media.

Many available commercial dispersants, such as those from BYK-Chemie,Efka Additives, and Lubrizol are well-suited to disperse pigments in avariety of liquid media. However, where it is applicable, for example,that a pigmented dispersion be used to make a coating, it is oftengenerally beneficial to include a polymer resin in the pigmenteddispersion to help reinforce the coated film, cohesively and adhesively,to the coating substrate. In the case where small registered drops on asubstrate are obtained, such as, for example, from continuous ink jetprinting or from drop on demand ink jet printing, a desired facet of animage can be improved upon, such as image gloss or rub, with theinclusion of a polymer resin in the pigmented dispersion or ink

Suitable carrier liquids or solvents that can be used to disperse thenanoscale-sized pigments with various polymers where solubility of thepolymers is ensured include, but are not limited to, acetone,acetonitrile, methyl acetate, ethyl acetate, n-butyl acetate,methoxypropylacetate, tetrahydrofuran, methanol, ethanol, n-propanol,iso-propanol, n-butanol, iso-butanol, sec-butanol, propylene glycolmonomethyl ether, ethylene glycol monomethyl ether, diethylene glycolmonomethyl ether, dipropylene glycol methyl ether, propylene glycolmethyl ether acetate, methyl ethyl ketone, methyl isobutyl, ketone,toluene, o-xylene, m-xylene, p-xylene, monochlorobenzene, chloromethane,dichloromethane, and the like. Of course, mixture of two or moresolvents and/or mixtures of two or more polymeric dispersants can beused, in embodiments, as desired. Thus, for example, it may be desirablein embodiments to use suitable mixtures of at least two solvents withone polymeric binder to effect dispersion and good coating ability ofthe nanoscale-sized pigments. It may also be desirable in embodiments touse suitable mixtures of at least two solvents with at least twopolymeric binders to effect dispersion and good coating ability of thenanoscale-sized pigments.

Other carrier liquids or solvents that can be used to disperse thenanoscale-sized pigments with various polymers where solubility of thepolymers or resins are ensured, include drying oils, mainly consistingof polyunsaturated fatty acids, such as tung oil, soy oil, linseed oil,safflower oil, sunflower oil, canola oil, poppy seed oil, perilla oil,oiticica oil, walnut oil, various fish oils, and suitable mixturesthereof. Still other carrier liquids or solvents that can be used todisperse the nanoscale-sized pigments with various polymers wheresolubility of the polymers or resins are ensured, include non-dryingoils such as paraffinic oils, naphthenic oils, isoparaffinic oils,neat's foot oil, rapeseed oil, cotton seed oil, castor oil, olive oil,coconut oil, silicone oils such as cyclomethicone and dimethicone,diester-based oils such as diisobutyl phthalate and dioctyl adipate,essential oils such as rose oil, and suitable mixtures thereof.

Suitable mixtures of various non-drying and drying oils may be used toadjust various physical properties of the carrier solvent systemincluding its viscosity, surface tension, evaporation rate, intrinsiccolor, oxidative stability at various temperatures, solvation power ofthe pigment dispersant and other binder additives that may be present,that include, but are not limited to, resins based on urethanes,phenolics such as phenol formaldehydes, phenolic esters, phenolic acidesters, maleics, acrylics, epoxides, tall oil fatty acids, naturalrosins and their derivatives such as rosin maleic esters, and the like.

Where it is deemed beneficial, suitable driers or drying agents such assoaps of cobalt, manganese, iron and vanadium, for example, can be usedto aid in the drying of oil-based compositions containingnanoscale-sized pigments as they are applied on a substrate, forexample, by ink jet printing. Examples of driers that aid in surfacedrying of the applied composition include cobalt octoate and manganesenaphthenate. Examples of driers that aid in depth drying, that is thedrying below the surface of the applied composition, are cerium octoate,zinc octoate and zirconium naphthenate. Usually it is preferable toinclude both surface and depth driers in oil-based compositionscontaining nanoscale-sized pigments to effect an evenly dried finalproduct and thus avoid wrinkling.

The nanoscale-sized pigments can be formulated into a number ofdifferent coating compositions having various adhesive and coloristicproperties on different media, including paperstock, cardstock, andflexible substrates including various poylolefin films, Melinex®,Mylar®, Cronar®, and the like, more rigid substrates as polyethylene,polypropylene and the like.

The applied coatings or images on various substrates can be dried underambient conditions, that is, they are self-drying, or by using variousair-forced drying chambers such as tunnels, by radiation, especiallyinfra-red radiation, or combinations of these processes.

Generally, the ink compositions contain one or more colorant. Anydesired or effective colorant can be employed in the ink compositions,including pigment, dye, mixtures of pigment and dye, mixtures ofpigments, mixtures of dyes, and the like. In embodiments, the colorantused in the ink composition consists entirely of the formednanoscale-sized pigment compositions. However, in other embodiments, thenanoscale-sized pigment compositions can be used in combination with oneor more conventional or other colorant material, where thenanoscale-sized pigment compositions can form substantially most of thecolorant material (such as about 90% or about 95% by weight or more),they can form a majority of the colorant material (such as at least 50%by weight or more), or they can form a minority of the colorant material(such as less than about 50% by weight). For the end-use application inpiezoelectric inkjet printing, nanosized pigment particles areadvantageous to ensure reliable inkjet printing and prevent blockage ofjets due to pigment particle agglomeration. In addition, nanosizedpigment particles are advantageous for offering enhanced colorproperties in printed images, since in embodiments the color propertiesof nanosized particles of monoazo laked pigment Red 57:1 were tunablewith particle size, whereby as average particle size (d₅₀) was decreasedto nanometer-scale, the hue angles were shifted from yellowish-red huesto bluish-red hues by an amount ranging from about 5 to 35° in the colorgamut space. In still other embodiments, the nanoscale-sized pigmentcompositions can be included in the ink composition in any other varyingamount, to provide either colorant and/or other properties to the inkcomposition.

The colorant, such as nanoscale-sized pigment compositions inembodiments, can be present in the ink composition in any desired oreffective amount to obtain the desired color or hue. For example, thecolorant can typically be present in an amount of at least about 0.1percent by weight of the ink, such as at least about 0.2 percent byweight of the ink or at least about 0.5 percent by weight of the ink,and typically no more than about 50 percent by weight of the ink, suchas no more than about 20 percent by weight of the ink or no more thanabout 10 percent by weight of the ink, although the amount can beoutside of these ranges.

The ink compositions can also optionally contain an antioxidant. Theoptional antioxidants of the ink compositions protect the images fromoxidation and also protect the ink components from oxidation during theheating portion of the ink preparation process. Specific examples ofsuitable antioxidants include NAUGUARD® series of antioxidants, such asNAUGUARD® 445, NAUGUARD® 524, NAUGUARD® 76, and NAUGUARD® 512(commercially available from Uniroyal Chemical Company, Oxford, Conn.),the IRGANOX® series of antioxidants such as IRGANOX® 1010 (commerciallyavailable from Ciba Geigy), and the like. When present, the optionalantioxidant can be present in the ink in any desired or effectiveamount, such as in an amount of from at least about 0.01 to about 20percent by weight of the ink, such as about 0.1 to about 5 percent byweight of the ink, or from about 1 to about 3 percent by weight of theink, although the amount can be outside of these ranges.

The ink compositions can also optionally contain a viscosity modifier.Examples of suitable viscosity modifiers include aliphatic ketones, suchas stearone, and the like. When present, the optional viscosity modifiercan be present in the ink in any desired or effective amount, such asabout 0.1 to about 99 percent by weight of the ink, such as about 1 toabout 30 percent by weight of the ink, or about 10 to about 15 percentby weight of the ink, although the amount can be outside of theseranges.

Other optional additives to the inks include clarifiers, such as UNIONCAMP® X37-523-235 (commercially available from Union Camp); tackifiers,such as FORAL® 85, a glycerol ester of hydrogenated abietic (rosin) acid(commercially available from Hercules), FORAL® 105, a pentaerythritolester of hydroabietic (rosin) acid (commercially available fromHercules), CELLOLYN® 21, a hydroabietic (rosin) alcohol ester ofphthalic acid (commercially available from Hercules), ARAKAWA KE-311Resin, a triglyceride of hydrogenated abietic (rosin) acid (commerciallyavailable from Arakawa Chemical Industries, Ltd.), synthetic polyterpeneresins such as NEVTAC® 2300, NEVTAC® 100, and NEVTAC® 80 (commerciallyavailable from Neville Chemical Company), WINGTACK® 86, a modifiedsynthetic polyterpene resin (commercially available from Goodyear), andthe like; adhesives, such as VERSAMID® 757, 759, or 744 (commerciallyavailable from Henkel), plasticizers, such as UNIPLEX® 250 (commerciallyavailable from Uniplex), the phthalate ester plasticizers commerciallyavailable from Monsanto under the trade name SANTICIZER®, such asdioctyl phthalate, diundecyl phthalate, alkylbenzyl phthalate(SANTICIZER® 278), triphenyl phosphate (commercially available fromMonsanto), KP-140®, a tributoxyethyl phosphate (commercially availablefrom FMC Corporation), MORFLEX® 150, a dicyclohexyl phthalate(commercially available from Morflex Chemical Company Inc.), trioctyltrimellitate (commercially available from Eastman Kodak Co.), and thelike; and the like. Such additives can be included in conventionalamounts for their usual purposes.

The ink composition also includes a carrier material, or mixture of twoor more carrier materials. The carrier material can vary, for example,depending upon the specific type of ink composition. For example,suitable solvents and carrier materials include those discussed above.

In still other embodiments, the present disclosure of nanopigmentparticles can be applied towards inks used in relief, gravure, stencil,and lithographic printing as well as towards various coatings ontosubstrates including, plastics, glasses, metals, and metallizedsubstrates, such as Aluminized Mylar®.

The ink compositions of the present disclosure can be prepared by anydesired or suitable method. For example, the ink ingredients can simplybe mixed together with stirring to provide a homogeneous composition,although heating can also be used if desired or necessary to help formthe composition.

An example is set forth herein below and is illustrative of differentcompositions and conditions that can be utilized in practicing thedisclosure. All proportions are by weight unless otherwise indicated. Itwill be apparent, however, that the disclosure can be practiced withmany types of compositions and can have many different uses inaccordance with the disclosure above and as pointed out hereinafter.

EXAMPLES Examples of Compositions and Method of Making Nanosized MonoazoLaked Red Pigment Comparative Example 1 Synthesis of Pigment Red 57:1Using a Two-Step Method

Step 1: Diazotization and Coupling:

Into a 500 mL round bottom flask equipped with a mechanical stirrer,thermometer, and addition funnel was dissolved2-amino-5-methylbenzenesulfonic acid (8.82 g) into 0.5M KOH aqueoussolution (97.0 mL). The resulting brown solution was cooled to 0° C. A20 wt % aqueous solution of sodium nitrite (NaNO₂; 3.28 g dissolved into25 mL water) was added slowly to the first solution while maintainingthe temperature below 3° C. To the red-brown homogeneous mixture wasadded dropwise concentrated HCl (10M, 14.15 mL) over 1 hour, maintainingthe internal temperature below 2° C. The mixture formed a pale brownsuspension, and following complete addition of conc. HCl, the suspensionwas stirred an additional 30 min.

In a separate 2-L resin kettle was dissolved 3-hydroxy-2-naphthoic acid(8.86 g) into an aqueous solution of KOH (8.72 g) in water (100 mL). Anadditional 250 mL of water was added, and the light-brown solution wasthen cooled to 15° C. while stirring vigorously. The cold suspension ofthe diazonium salt suspension was then added slowly to the couplingsolution while mixing vigorously. The color changed initially to a darkred solution, and ultimately to a yellowish-red (orange) slurry ofprecipitated dyestuff. The mixture was stirred for 2 hours while warmingup to room temp, then filtered and diluted with about 500 mL ofdeionized water to produce an orange aqueous slurry of LitholRubine-Potassium salt dye (a synthetic precursor of Pigment Red57:1)having solids content of about 1.6 wt %.

Step 2: Laking Step to Produce Pigment Red 57:1 Particles

Into a 500 mL round bottom flask equipped with mechanical stirrer andcondenser was charged 126 g of aqueous slurry of Lithol Rubine-Potassiumsalt dye precursor from above having about 1.6% wt solids content. ThepH of the slurry was adjusted to at least 9.0 or higher by addition of0.5 M KOH solution, after which the dyestuff was fully dissolved. Anaqueous solution of calcium chloride dihydrate (0.5 M solution, 13 mL)was added dropwise to the slurry while stirring vigorously. A redprecipitate formed immediately, and after addition was completed, theslurry was stirred for an additional 1 hour. The red slurry was thenheated to about 75° C. for 20 min, then cooled to room temp. The slurrywas filtered under high vacuum through a 1.2 μm acrylic polymermembrane, then reslurried twice with 200 mL portions of deionized water.The pH and conductivity of the filtrates after each filtration weremeasured and recorded, with the final wash filtrate having nearlyneutral pH of 6.2 and conductivity of about 13.5 μS/cm, indicating lowresidual salts. The red pigment filtercake was reslurried into about 200mL of DIW and freeze-dried for 48 hours, to afford a red colored powder(1.95 grams). TEM microscopy revealed long rod-like particles andaggregates, with particle diameters ranging from about 200 nm to about700 nm, and large aspect ratios ranging from about 4:1 to about 10:1.

Comparative Example 2 Synthesis of Pigment Red 57:1 using a One-StepMethod

Diazotization Mixture: Into a 100 mL round bottom flask equipped with amechanical stirrer, thermometer, and addition funnel was added2-amino-5-methylbenzenesulfonic acid (2.2 g), deionized water (22 mL)and concentrated ammonia (30 wt %; 1.5 g). The resulting light brownsolution was cooled to −2° C. An aqueous solution of sodium nitrite(NaNO₂; 0.82 g dissolved into 3 mL water) was added slowly to the firstsolution while maintaining the temperature below 2° C. To thereddish-brown homogeneous mixture was added dropwise concentrated HCl(3.6 g) so as to maintain the internal temperature below 2° C. Themixture formed a pale brown suspension, and following complete additionof conc. HCl, the suspension was stirred an additional 30 min. Asolution of calcium chloride dehydrate (2.6 g) dissolved into deionizedwater (5 mL) was added to the diazo suspension

Coupling Mixture: In a separate 500 mL flask equipped with high-speedmechanical stirrer, thermometer and dropping funnel was added3-hydroxy-2-naphthoic acid (2.3 g), deionized water (60 mL), andconcentrated ammonia (30 wt %, 1.5 g). After stirring to dissolution, anaqueous solution of 5 wt % Dresinate-X rosin surfactant (10 mL) wasadded and the mixture stirred to dissolution.

The cold suspension of the diazonium salt suspension was then addedslowly to the coupling solution under vigorous mixing. The color changedto a red slurry of precipitated pigment particles. The mixture wasstirred for 30 minutes, then vacuum-filtered through a 0.8 μm acrylicpolymer membrane, reslurried once with 300 mL of DIW and filtered again.The red pigment 57:1 filtercake was reslurried into about 250 mL of DIWfor a final time, and freeze-dried for 48 hours to afford a red powder(3.55 grams). TEM micrograph images showed a distribution of longplatelet-like particles with diameters ranging from 200 to 500 nm, andlarge aspect ratios ranging from about 4:1 to about 10:1.

Example 1 Synthesis of Nano-Sized Particles of Pigment Red 57:1 by aTwo-Step Method

Step 1: Diazotization and Coupling:

Into a 500 mL round bottom flask equipped with a mechanical stirrer,thermometer, and addition funnel was dissolved2-amino-5-methylbenzenesulfonic acid (8.82 g) into 0.5M KOH aqueoussolution (97.0 mL). The resulting brown solution was cooled to 0° C. A20 wt % aqueous solution of sodium nitrite (NaNO₂; 3.28 g dissolved into25 mL water) was added slowly to the first solution while maintainingthe temperature below 3° C. To the red-brown homogeneous mixture wasadded dropwise concentrated HCl (10M, 14.15 mL) over 1 hour, maintainingthe internal temperature below 2° C. The mixture formed a pale brownsuspension, and following complete addition of conc. HCl, the suspensionwas stirred an additional 30 min.

In a separate 2-L resin kettle was dissolved 3-hydroxy-2-naphthoic acid(8.86 g) into an aqueous solution of KOH (8.72 g) in water (100 mL). Anadditional 250 mL of water was added, and the light-brown solution wasthen cooled to 15° C. while stirring vigorously. The cold suspension ofthe diazonium salt suspension was then added slowly to the couplingsolution while mixing vigorously. The color changed immediately to adark red solution, and ultimately to a yellowish-red (orange) slurry ofprecipitated dyestuff. The mixture was stirred for 2 hours while warmingup to room temp, then filtered and reslurried with about 500 mL ofdeionized water to produce an orange aqueous slurry of LitholRubine-Potassium salt dye having solids content of about 1.6 wt %.

Step 2: Laking Step to Produce Pigment Red 57:1 Particles:

Into a 500 mL round bottom flask equipped with mechanical stirrer andcondenser was charged 126 g of aqueous slurry of Lithol Rubine-Potassiumsalt dye from above (Example 1, Step 1) having about 1.6% wt solidscontent. The pH of the slurry was adjusted to at least 9.0 or higher byaddition of 0.5 M KOH solution, after which the dyestuff was fullydissolved. An aqueous solution 5 wt % Dresinate X (4.0 mL) was added,followed by a solution containing sodium dioctyl sulfosuccinate (0.96 g)dissolved in 100 mL of 90:10 deionized water/THF mixture. No visiblechange was observed. An aqueous solution of calcium chloride dihydrate(0.5 M solution, 13 mL) was added dropwise to the slurry while stirringvigorously. A red precipitate formed immediately, and after completeaddition of the calcium chloride solution, the slurry was stirred for anadditional 1 hour. The red slurry was then heated to about 75° C. for 20min, then cooled to room temp. The slurry was filtered under high vacuumthrough a 0.45 μm Nylon membrane cloth, then reslurried twice with 75 mLportions of DIW. The pH and conductivity of the final wash filtrate was7.4 and about 110 μS/cm, respectively, indicating that residual acidsand salt by-products were removed. The red pigment filtercake wasreslurried in about 250 mL of DIW and freeze-dried for 48 hours toafford a dark red colored powder (2.65 grams). Transmission electronmicroscopy images of the powder revealed platelet-like particles withparticle diameters ranging from 30-150 nm, and aspect ratios that wereless than 3:1. ¹H-NMR spectroscopy analysis (300 MHz, DMSO-d₆) of thepigment indicated that the pigment adopted the hydrazone tautomer form,and that the dioctyl sulfosuccinate stabilizer compound was present atapproximately 40 mol % (representing about 80% remaining of actualloading) and was associated with a calcium cation (determined by ICPspectroscopy).

Example 2 Synthesis of Nano-Sized Particles of Pigment Red 57:1 by aTwo-Step Method

The procedure of Step 1 of Example 1 above was reproduced.

Step 2: Laking

Into a 500 mL round bottom flask equipped with mechanical stirrer andcondenser was charged 126 g of aqueous slurry of Lithol Rubine-Potassiumsalt dye from above (Example 1) having about 1.6% wt solids content. ThepH of the slurry was adjusted to at least 9.0 or higher by addition of0.5 M KOH solution, after which the dyestuff was fully dissolved. Anaqueous solution 5 wt % Dresinate X (4.0 mL) was added, followed by asolution containing sodium dioctyl sulfosuccinate (0.96 g) dissolved in100 mL of 90:10 deionized water/THF mixture. No visible change wasobserved. An aqueous solution of calcium chloride dihydrate (0.5 Msolution, 13 mL) was added dropwise to the slurry while stirringvigorously. A red precipitate formed immediately, and after completeaddition of the calcium chloride solution, the slurry was stirred for anadditional 1 hour. The red slurry was then heated to about 75° C. for 20min, then cooled to room temp. The slurry was filtered under high vacuumthrough a 0.45 μm Nylon membrane cloth, then reslurried twice with 75 mLportions of DIW. The pH and conductivity of the final wash filtrate was7.15 and about 155 μS/cm, respectively. The red pigment filtercake wasreslurried in about 250 mL of DIW and freeze-dried for 48 hours toafford a dark red-colored powder (2.62 grams). Transmission electronmicroscopy images of the powder revealed platelet-like particles withparticle diameters ranging from 50-175 nm, and aspect ratios equal to orless than 3:1

Example 3 Synthesis of Nano-Sized Particles of Pigment Red 57:1 by aTwo-Step Method

Step 1: Diazotization and Coupling:

Into a 500 mL round bottom flask equipped with a mechanical stirrer,thermometer, and addition funnel was dissolved2-amino-5-methylbenzenesulfonic acid (12.15 g) into 0.5M KOH aqueoussolution (135 mL). The resulting brown solution was cooled to 0° C. A 20wt % aqueous solution of sodium nitrite (NaNO₂; 4.52 g dissolved into 30mL water) was added slowly to the first solution while maintaining thetemperature below −2° C. Concentrated HCl (10M, 19.5 mL) was then slowlyadded dropwise over 1 hour while maintaining the internal temperaturebelow 0° C. The mixture formed a pale brown suspension and followingcomplete addition of conc. HCl, the suspension was stirred an additional30 min.

In a separate 2-L resin kettle was dissolved 3-hydroxy-2-naphthoic acid(12.2 g) into an aqueous solution of KOH (12.0 g) in water (130 mL). Anadditional 370 mL of water was added, and the pale brown solution wasthen cooled to about 15° C. while stirring. The cold suspension of thediazonium salt solution was then added slowly to the coupling solutionwhile mixing vigorously. The color change was immediate to darkblack-red solution, and ultimately to a yellowish-red (orange) slurry ofprecipitated dyestuff. The mixture was stirred for at least 2 hourswhile warming up to room temp, then filtered and reslurried with about600 mL of deionized water to produce an orange-colored slurry of LitholRubine-Potassium salt dye having solids content of about 3.75%-wt.

Step 2: Laking Step to Produced Nano-Sized Particles of Pigment Red 57:1

Into a 1-L resin kettle equipped with mechanical stirrer and condenserwas charged 265 g of aqueous slurry of Lithol Rubine-Potassium salt dyeprepared from Step 1 of Example 2 above, having approximately 3.75%-wtsolids content). The pH of the slurry was adjusted to at least 9.0 orhigher by addition of 0.5 M KOH solution, after which the dyestuff wasfully dissolved. An aqueous solution 5 wt % Dresinate X (20.0 mL) wasadded while stirring, followed by a solution containing sodium dioctylsulfosuccinate (4.8 g) dissolved in 220 mL of 90:10 deionized water/THFmixture was slowly added to the mixture with stirring. An aqueoussolution of calcium chloride dihydrate (0.5 M solution, 65 mL) was addeddropwise to the slurry while stirring vigorously. A red precipitateformed immediately, and after complete addition of the calcium chloridesolution, the slurry was stirred for an additional 1 hour. The redslurry was then heated to about 60° C. for 30 min, then cooledimmediately in a cold water bath. The slurry was filtered under highvacuum through a 0.8 micron Versapor membrane cloth (obtained from PALLCorp.), then reslurried twice with about 750 mL portions of DIW, andfiltered once more. The pH and conductivity of the final wash filtratewas 7.5 and about 208 μS/cm, respectively. The red pigment filtercakewas reslurried in about 600 mL of deionized water and freeze-dried for48 hours, to afford a dark red-colored powder (12.75 grams).Transmission electron microscopy images of the powder revealedpredominantly platelet-like particles with particle diameters rangingfrom 50-150 nm, and aspect ratios that were equal to or less than about3:1

Example 4 Preparation of Nano-Sized Particles of Pigment Red 57:1 usingthe Two-Step Method

Into a 250 mL round bottom flask equipped with mechanical stirrer andcondenser was charged 10 g of aqueous slurry of Lithol Rubine-Potassiumsalt dye precursor prepared as in Step 1 of Example 3, except that thesolids concentration in the aqueous slurry was about 10.0 wt %. The pHof the slurry was adjusted to at least 9.0 or higher by addition of 0.5M KOH solution, after which the dyestuff was fully dissolved. An aqueoussolution 5 wt % Dresinate X (1.0 mL) was added, followed by a 0.05 mol/Lsolution (34.5 mL) containing sodium dioctyl sulfosuccinate dissolved in90:10 deionized water/THF. No visible change was observed. An aqueoussolution of calcium chloride dihydrate (1.0 M solution, 2.15 mL) wasadded dropwise by syringe pump to the slurry while stirring vigorously.A red precipitate formed immediately, and then the slurry was stirred atroom temperature for an additional 30 min. The red slurry was thenfiltered under high vacuum through a 0.8 μm Versapor membrane cloth(obtained from PALL Corp.), then reslurried twice with 50 mL portions ofdeionized water and filtered each time after reslurrying. The pH andconductivity of the final wash filtrate was 7.5 and about 135 μS/cm,respectively, indicating that residual acids and salt by-products wereremoved. The red pigment filtercake was reslurried in about 30 mL ofdeionized water and freeze-dried for 48 hours to afford a dark redcolored powder (1.32 grams). Transmission electron microscopy images ofthe powder revealed very small platelet-like particles with particlediameters ranging from 50-175 nm, and aspect ratios were equal to orless than about 3:1. ¹H-NMR spectroscopy analysis (300 MHz, DMSO-d₆) ofthe material indicated that the pigment adopted the hydrazone tautomerform, and that the dioctyl sulfosuccinate stabilizer compound waspresent at a level ranging from approximately 50-75 mol %.

Example 5 Preparation of Fine and Nano-Sized Particles of Pigment Red57:1 using the Two-Step Method

Into a 500 mL round bottom flask equipped with mechanical stirrer andcondenser was charged 126 g of aqueous slurry of Lithol Rubine-Potassiumsalt dye precursor (prepared as in Step 1 of Example 1) having about1.6% wt solids content. The pH of the slurry was adjusted to at least9.0 or higher by addition of 0.5 M KOH solution, after which thedyestuff was fully dissolved. An aqueous solution 5 wt % Dresinate X(4.0 mL) was added, followed by a solution containing sodium dioctylsulfosuccinate (1.92 g) dissolved in 100 mL of 90:10 deionized water/THFmixture. No visible change was observed. An aqueous solution of calciumchloride dihydrate (0.5 M solution, 13 mL) was added dropwise to theslurry while stirring vigorously. A red precipitate formed immediately,and after complete addition of the calcium chloride solution, the slurrywas stirred for an additional 1 hour. The red slurry was then heated toabout 75° C. for 20 min, then cooled to room temp. The slurry wasfiltered under high vacuum through a 0.45 μm Nylon membrane cloth, thenreslurried twice with 75 mL portions of DIW. The pH and conductivity ofthe final wash filtrate was 7.75 and conductivity of about 500 μS/cm.The red pigment filtercake was reslurried in about 250 mL of DIW andfreeze-dried for 48 hours to afford a dark red-colored powder (2.73grams). Transmission electron microscopy images of the powder showed adistribution of particle sizes, with diameter ranging from 50 to 400 nmand having particle morphologies that were predominantly platelets.

Example 6 Preparation of Fine and Nanosized Particles of Pigment Red57:1 using a Two-Step Method

The sterically bulky stabilizer compound used was potassium salt of2-hexyldecanoic acid, prepared by treatment of 2-hexyldecanoic acid withpotassium hydroxide dissolved in THF, after which the THF solvent wasremoved. Into a 500-mL round-bottom flask equipped with condenser andmechanical stirrer was charged 126 g of aqueous slurry of LitholRubine-Potassium salt (prepared as in Step 1 of Example 1) having about1.6% wt solids content. The pH of the slurry was adjusted to at least9.0 or higher by addition of 0.5 M KOH solution, after which thedyestuff was fully dissolved. An aqueous solution 5 wt % Dresinate X(4.0 mL) was added, followed by a solution containing potassium2-hexyldecanoate (1.28 g) dissolved in 100 mL of 80:20 deionizedwater/THF mixture, added dropwise while stirring vigorously. An aqueoussolution of calcium chloride dihydrate (0.5 M solution, 13 mL) was addedto the slurry while stirring vigorously causing a bluish-red pigmentprecipitate to form. The slurry was stirred for 1 hour, heated to about75° C. for 20 min, then cooled to room temperature. The slurry wasfiltered under high vacuum through a 0.8 μm Nylon membrane cloth, thenreslurried once with 150 mL of DIW and filtered again. The pH andconductivity of the final wash filtrate was pH 8.38 and conductivity ofabout 63 μS/cm. The red pigment 57:1 filtercake was reslurried intoabout 150 mL of DIW and freeze-dried for 48 hours to afford a red powder(2.95 grams). TEM micrograph images showed a distribution of particlesizes, with diameters ranging from 50 to about 400 nm and havingparticle morphologies that included platelets as well as rods.

Example 7 Synthesis of Nano-Sized Particles of Pigment Red 57:1 by aOne-Step Procedure

Diazotization Mixture: Into a 100 mL round bottom flask equipped with amechanical stirrer, thermometer, and addition funnel was added2-amino-5-methylbenzenesulfonic acid (4.4 g), deionized water (45 mL)and concentrated ammonia (30 wt %; 3.0 g). The resulting light brownsolution was cooled to −2° C. An aqueous solution of sodium nitrite(NaNO₂; 1.64 g dissolved into 6 mL water) was added slowly to the firstsolution while maintaining the temperature below 3° C. To thereddish-brown homogeneous mixture was added dropwise concentrated HCl(7.2 g) so as to maintain the internal temperature below 2° C. Themixture formed a pale brown suspension, and following complete additionof conc. HCl, the suspension was stirred an additional 30 min. Asolution of calcium chloride dehydrate (5.20 g) dissolved into deionizedwater (10 mL) was added to the diazo suspension.

Coupling Mixture: In a separate 500 mL flask equipped with high-speedmechanical stirrer, thermometer and dropping funnel was added3-hydroxy-2-naphthoic acid (4.60 g), deionized water (120 mL), andconcentrated ammonia (30 wt %, 3.0 g). After stirring to dissolution, anaqueous solution of 5 wt % Dresinate-X rosin soap surfactant (20 mL) wasadded, followed with a prepared solution containing sodium dioctylsulfosuccinate (5.25 g) dissolved in 56 mL of 90:10 deionized water/THFmixture.

The cold suspension of the diazonium salt suspension was then addedslowly to the coupling solution under vigorous mixing. The color changedimmediately to a dark red solution, and ultimately to a bluish-redslurry of precipitated pigment particles. The mixture was heated at 50°C. for 15 minutes, then cooled to room temperature. The slurry wasfiltered under high vacuum through a 0.8 μm acrylic membrane cloth, thenreslurried once with 400 mL of DIW and filtered again. The red pigment57:1 filtercake was reslurried into about 200 mL of DIW and freeze-driedfor 48 hours to afford a red powder (8.73 grams). TEM micrograph imagesshowed a distribution of particles with diameters ranging from 50 to 300nm, the majority of which were less than 200 nm in diameter, and havingparticle morphologies that were generally platelets, and having aspectratio that were equal to or less than about 3:1.

Examples of Pigment Dispersions and Their Properties Example 8Preparation of Liquid Pigment Dispersions and Polymer Coatings

A series of liquid, non-aqueous dispersions were prepared using apolymeric dispersant and the nano-sized PR 57:1 pigments from Examples1, 2, 3, 4, 5 and 6; the larger-sized pigment particles prepared asdescribed in the Comparative Example 1; as well as two commercialsources of PR 57:1 obtained from Clariant (lot #L7B01) and Aakash.Coatings on clear Mylar film were prepared from these liquiddispersions, and evaluated in the following manner: Into a 30 mL amberbottle was added 0.22 g of pigment, 0.094 g polyvinylbutyral (B30HHobtained from Hoescht), 7.13 g n-butyl acetate (glass-distilled grade,obtained from Caledon Laboratories) and 70.0 g of ⅛″ stainless steelshot (Grade 25 440C obtained from Hoover Precision Products). Thebottles were transferred to a jar mill and were allowed to gently millfor 4 days at 100 RPM. Two draw-down coatings were obtained for eachdispersion using an 8-path gap on clear Mylar film such that the wetthicknesses for each coating comprised of PR 57:1 pigment sample were0.5 and 1 mil. The air-dried coatings on clear Mylar film were thendried in a horizontal forced-air oven at 100° C. for 20 minutes.

Example 9 Evaluation of Coatings Prepared from Liquid PigmentDispersions

The coatings on clear Mylar film prepared as described in Example 8 wereassessed for coloristic and light scattering properties in the followingmanner: The UV/VIS/NIR transmittance spectra of each coating wereobtained using a Shimadzu UV160 spectrophotometer, and the resultsshowed dramatically reduced light scattering and remarkable specularreflectivity for the nano-sized PR 57:1 pigment samples describedherein, compared with the spectra of coatings prepared with commercialPR 57:1 pigment samples obtained from Clariant and Aakash. The degree oflight scattering in a coating is dependent on both the size and shapedistributions of the pigment particles and their relative dispersabilitywithin the coating matrix, and the Normalized Light Scatter Index (NLSI)method was developed to be a measure of this characteristic for thepigmented coatings. NLSI is quantified by first measuring the spectralabsorbance of the coating in a region where there is no absorbance fromthe chromogen of the monoazo laked pigment (for PR 57:1, a suitableregion is 700-900 nm), but only absorbance due to light scattered fromlarge aggregates and/or agglomerated pigment particles dispersed in thecoating binder. The Normalized Light Scatter Index (NLSI) is thenobtained by normalizing each of the samples' light scattering indices(from 700 to 900 nm) to a lambda-max optical density=1.5. In this way,the degree of light scattering for each pigmented coating could becompared directly against each other. The lower the NLSI value, thesmaller the inferred particle size of the dispersed pigment in thecoating. A relationship between decreasing average particle size anddecreasing NLSI value was found to exist with the coatings prepared fromthe example pigments shown in Table 8. In particular, the nano-sizedmonoazo laked pigment PR 57:1 of Example 1 had by far the lowest degreeof light scattering, with an NLSI value of 0.3. The coloristicproperties of the Mylar coatings were determined using an X-RITE 938spectrodensitometer. L* a* b* and optical density (O.D.) values wereobtained for each of the samples, and the L* a* b* were normalized to anoptical density of 1.5, and used to calculate the hue angle and chroma(c*), as listed in Table 8.

TABLE 8 Normalized Light Scatter Indices (NLSI) and Coloristicproperties of example PR 57:1 pigments, normalized to O.D. = 1.5Clariant L7B Aakash Comparative Metric 01 PR57:1 Example 1 Example 1Example 2 Example 3 Example 4 Example 5 Example 6 L* 47.9 48.0 44.8 50.850.6 51.7 53.0 49.9 49.6 a* 71.1 71.2 71.5 76.5 77.2 79.4 78.8 76.7 73.6b* 8.7 17.5 34.8 −16.4 −17.4 −18.8 −15.0 −18.9 1.4 Hue Angle (°) 6.613.8 28.1 347.9 347.1 346.6 349.2 346.1 0.9 C* 72.6 73.4 78.1 78.6 77.581.3 80.5 78.9 73.9 Normalized 5.5 9.9 74.1 0.3 1.3 1.0 0.7 0.9 4.8Light Scatter Index

Example 10 b*a* Coloristic Properties of Coatings Prepared from LiquidPigment Dispersions

The graphs in FIGS. 1 and 2 visually illustrate the significant shiftsin b* a* gamut observed with coatings prepared with the nano-sized PR57:1 pigments from Examples 1, 2, 3, 4 and 5, in addition to theextended c* chroma for the nano-sized pigment examples. Furthermore, thegraph in FIG. 1 shows a clear blue-shifting of hue that directlycorresponds to decreasing particle size/particle diameters of theexample PR 57:1 pigments, a relationship which is also inferred from theNormalized Light Scatter Index (NLSI) values of Table 8. (Note: For easeof generating the graph, the b* vertical axis shows “negative” hueangles, which represent the number of degrees <360 degrees.) The lightscattering and coloristic data accumulated provide evidence for theability to tune color properties and specular reflectivity of pigmentedcoatings with tunable particle size of surface-enhanced fine particlesof monoazo laked red pigments, in particular Pigment Red 57:1. This isachieved by using the methods of making such nano-sized pigments of PR57:1 as described herein, in particular using the two-step process whichuses sterically bulky stabilizer compounds to limit particle aggregationand thereby limit particle size as well as enhance dispersion and colorcharacteristics of the nano-sized pigment particles. Furthermore, theability to easily tune color properties of such monoazo laked pigmentsprovides a means to control the color quality so that inexpensive azolaked pigments like PR 57:1 can be used to obtain magenta color that arenormally exhibited by higher cost red pigments, such as thequinacridone-type Pigment Red 122 and Pigment Red 202.

Example 12 Preparation of Liquid Dispersions Containing Oils

Into a 30 mL glass amber bottle are added 0.20 g of nanopigment fromExample 1, 0.21 g Solsperse® 13940 (available from Lubrizol), 0.22 gWingtack® 86 resin (available from Sartomer Company), 6.03 g linseed oil(available from Sigma-Aldrich), 1.62 g Isopar® G (available from UnivarUSA), 0.016 g Cobalt octotate (available from Troy Corporation) and 70.0g of ⅛″ stainless steel shot (Grade 25 440C obtained from HooverPrecision Products). The bottle is transferred to a jar mill and allowedto gently mill for 4 days at about 100 RPM. Two draw-down coatings areobtained for each dispersion using an 8-path gap on clear Mylar® filmsuch that the wet thicknesses for each coating comprised of PR57:1pigment sample were 0.5 and 1 mil. The coatings on clear Mylar® film arethen dried in a horizontal forced-air oven at 135° C. for 20 minutes.The resultant coated films containing nano-sized PR57:1 pigment areuniform and exhibit high gloss.

Example 13 Preparation of Liquid Dispersions Containing a Ketone andEster

Into a 30 mL glass amber bottle are added 0.17 g of nanopigment fromExample 1, 0.33 g Solsperse® 34750 (available from Lubrizol), 0.11 gpolyvinylbutyral (B30HH obtained from Hoechst) 4.48 g acetone, 1.94 gmethyl ethyl ketone (both solvents available from Caledon Laboratories),and 70.0 g of ⅛″ stainless steel shot (Grade 25 440C obtained fromHoover Precision Products). The bottle is transferred to a jar mill andallowed to gently mill for 4 days at about 100 RPM. Two draw-downcoatings are obtained for each dispersion using an 8-path gap on clearMylar® film such that the wet thicknesses for each coating comprised ofPR57:1 pigment sample were 0.5 and 1 mil. The coatings on clear Mylar®film are then dried in a horizontal forced-air oven at 100° C. for 20minutes. The resultant coated films containing nano-sized PR57:1 pigmentare uniform and exhibit high gloss

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A non-aqueous dispersion composition comprising: a non-aqueouscarrier, a polymeric dispersant, a polymer resin, and a nanoscalepigment particle composition comprising: an organic monoazo lakedpigment having at least one functional moiety, and a sterically bulkystabilizer compound having at least one functional group, wherein thefunctional moiety of the pigment associates non-covalently with thefunctional group of the stabilizer; and presence of the associatedstabilizer limits an extent of particle growth and aggregation, so as toafford nanoscale-sized pigment particles.
 2. The composition of claim 1,wherein the nanoscale pigment particle composition imparts color to thenon-aqueous dispersion composition.
 3. The composition of claim 1,wherein the carrier is present in an amount of about 50 to about 99.9weight %, and said nanoscale pigment particle composition is present inan amount of about 0.1 to about 50 weight % by weight of the non-aqueousdispersion composition.
 4. The composition of claim 1, wherein thepolymeric dispersant is selected from the group consisting ofderivatives of rosin natural products, acrylic-based polymers,styrene-based copolymers, copolymers of α-olefins, copolymers of vinylpyridine, vinyl imidazole, vinyl pyrrolidinone, polyester copolymers,polyamide copolymers, copolymers of acetals, poly(vinyl butyral-co-vinylalcohol-co-vinyl acetate), poly(vinyl acetate), poly(acrylic acid),poly(methacrylic acid), poly(vinyl alcohol), poly(N-vinylcarbazole),poly(methyl methacrylate), polyvinylidene difluoride, polyesters,polycarbonate polymers, poly(2-hydroxyethyl methacrylate),poly(styrene-b-4-vinylpyridine), polyurethane resins,polyetheretherketones, phenol-formaldehyde resins, polyols, glycolicpolymers, polysulfones, polyarylethers, and polyarylsulfones.
 5. Thecomposition of claim 1, wherein the polymeric dispersant is selectedfrom the group consisting of copolymers of 1-hexadecene, copolymers of1-octadecene, copolymers of 1-eicosene, copolymers of 1-triacontene,poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), poly(vinylacetate), poly(acrylic acid), poly(methacrylic acid), poly(vinylalcohol), poly(methyl methacrylate), polyester, polycarbonate,poly(styrene-b-4-vinylpyridine), polyethylene glycol polymers and theirderivatives, and mixtures thereof.
 6. The composition of claim 1,wherein the carrier is selected from the group consisting of acetone,acetonitrile, methyl acetate, ethyl acetate, n-butyl acetate,methoxypropylacetate, tetrahydrofuran, methanol, ethanol, n-propanol,iso-propanol, n-butanol, iso-butanol, sec-butanol, propylene glycolmonomethyl ether, ethylene glycol monomethyl ether, diethylene glycolmonomethyl ether, dipropylene glycol methyl ether, propylene glycolmethyl ether acetate, methyl ethyl ketone, methyl isobutyl, ketone,toluene, o-xylene, m-xylene, p-xylene, monochlorobenzene, chloromethane,dichloromethane, drying oils, non-drying oils, and mixtures thereof. 7.The composition of claim 1, wherein the composition is an inkcomposition.
 8. The composition of claim 1, further comprising at leastone additive selected from the group consisting of surfactants, lightstabilizers, UV absorbers, optical brighteners, thixotropic agents,dewetting agents, slip agents, foaming agents, antifoaming agents, flowagents, oils, plasticizers, binders, electrical conductive agents,fungicides, bactericides, organic and inorganic filler particles,leveling agents, opacifiers, antistatic agents, dispersants, dryingagents, and mixtures thereof.
 9. The composition of claim 1, furthercomprising an additional colorant different from said nanoscale pigmentparticle composition, selected from the group consisting of pigment,dye, mixtures of pigment and dye, mixtures of pigments, mixtures ofdyes, and the like.
 10. The composition of claim 1, wherein thenanoscale-sized pigment particles have an average particle diameter, asderived from transmission electron microscopy imaging, of less thanabout 200 nm.
 11. The composition of claim 1, wherein the at least onefunctional moiety of the organic monoazo laked pigment is selected fromthe group consisting of sulfonate/sulfonic acid,(thio)carboxylate/(thio)carboxylic acid, phosphonate/phosphonic acid,ammonium and substituted ammonium salts, phosphonium and substitutedphosphonium salts, substituted carbonium salts, substituted aryliumsalts, alkyl/aryl (thio)carboxylate esters, thiol esters, primary andsecondary amides, primary and secondary amines, hydroxyl, ketone,aldehyde, oxime, hydroxylamino, enamines, porphyrins, (phthalo)cyanines,urethane, carbamate, substituted ureas, guanidines and guanidiniumsalts, pyridine and pyridinium salts, imidazolium and (benz)imidazoliumsalts, (benz)imidazolones, pyrrolo, pyrimidine and pyrimidinium salts,pyridinone, piperidine and piperidinium salts, piperazine andpiperazinium salts, triazolo, tetraazolo, oxazole, oxazolines andoxazolinium salts, indoles, indenones, and mixtures thereof.
 12. Thecomposition of claim 1, wherein the organic monoazo laked pigmentcomprises a diazonium component linked to a coupling component throughan azo or hydrazone group, with a counterion.
 13. The composition ofclaim 12, wherein a precursor to the diazonium component of the monoazolaked pigment is a compound of Formula (2):

where R₁, R₂, and R₃ independently represent H, a straight or branchedalkyl group of from about 1 to about 10 carbon atoms, halogen, NH₂, NO₂,CO₂H, or CH₂CH₃; and FM represents SO₃H, —C(═O)—NH-Aryl-SO₃ ⁻ (whereAryl represents an aryl group that can be unsubstituted or substitutedwith either halogens or alkyl groups having from about 1 to about 10carbons), CO₂H, halogen, NH₂, or —C(═O)—NH₂, or is a compound of Formula(3):


14. The composition of claim 13, wherein the precursor to the diazoniumcomponent is selected from the group consisting of the followingcompounds of Formula (2) wherein: FM is SO₃H, R₁ is CH₃, R₂ is H, and R₃is NH₂, FM is SO₃H, R₁ is CH₃, R₂ is Cl, and R₃ is NH₂, FM is SO₃H, R₁is Cl, R₂ is CH₃, and R₃ is NH₂, FM is SO₃H, R₁ is Cl, R₂ is CO₂H, andR₃ is NH₂, FM is SO₃H, R₁ is Cl, R₂ is CH₂CH₃, and R₃ is NH₂, FM isSO₃H, R₁ is Cl, R₂ is Cl, and R₃ is NH₂, FM is SO₃H, R₁ is H, R₂ is NH₂,and R₃ is H, FM is SO₃H, R₁ is H, R₂ is NH₂, and R₃ is CH₃, FM is SO₃H,R₁ is NH₂, R₂ is H, and R₃ is Cl, FM is SO₃H, R₁ is H, R₂ is H, and R₃is NH₂, FM is SO₃H, R₁ is H, R₂ is NH₂, and R₃ is H, FM is SO₃H, R₁ isNO₂, R₂ is NH₂, and R₃ is H, FM is —C(═O) —NH-Phenyl-SO ₃ ⁻, R₁ is NH₂,R₂ is CH₃, and R₃ is H, FM is CO₂H, R₁ is H, R₂ is H, and R₃ is NH₂, FMis Cl, R₁ is H, R₂ is H, and R₃ is NH₂, FM is NH₂, R₁ is CH₃, R₂ is H,and R₃ is H, FM is NH₂, R₁ is H, R₂ is CH₃, and R₃ is H, FM is—C(═O)NH₂, R₁ is NH₂, R₂ is CH₃, and R₃ is H, FM is —C(═O)NH₂, R₁ is H,R₂ is NH₂, and R₃ is H, and FM is NH₂, R₁ is H, R₂ is H, and R₃ is H.15. The composition of claim 12, wherein a precursor to the couplingcomponent of the monoazo laked pigment is selected from the groupconsisting of β-naphthol and derivatives thereof, naphthalene sulfonicacid derivatives, pyrazolone derivatives, and acetoacetic arylidederivatives.
 16. The composition of claim 12, wherein a precursor to thecoupling component is selected from the group consisting of compounds ofFormulas (4)-(8), wherein * denotes a point of coupling or attachment tothe azo or hydrazone group:

where FM represents H, CO₂H, SO₃H, —C(═O)-NH-Aryl-SO₃ ⁻ where the arylgroup can be unsubstituted or substituted with either halogens, or alkylgroups having from about 1 to about 10 carbons, CO₂H, halogen, NH₂,—C(═O)—NH₂, substituted benzamides, or benzimidazolone amides;

where FM represents SO₃H, CO₂H, —C(═O)-NH-Aryl-SO₃ ⁻ where the arylgroup can be unsubstituted or substituted with either halogens, or alkylgroups having from about 1 to about 10 carbons, CO₂H, halogens, NH₂,—C(═O)—NH₂ groups R₃ and R₄ independently represent H, SO₃H;

where FM represents SO₃H, CO₂H, —C(═O) —NH-Aryl-SO₃ ⁻ where the arylgroup can be unsubstituted or substituted with either halogens, or alkylgroups having from about 1 to about 10 carbons, CO₂H, halogens, NH₂,—C(═O) —NH₂; R₁, R₂, R₃ and R₄ independently represent H, SO₃H,—C(═O)—NH-Phenyl;

where G represents CO₂H, straight or branched alkyl having from 1 toabout 10 carbons atoms; and R₁′, R₂′, R₃′ and R₄′ independentlyrepresent H, halogens, SO₃H, NO₂ or alkoxyl groups;

where R₁′ represents a straight or branched alkyl group having from 1 toabout 10 carbon atoms, R₂′ represents

where each of R_(a), R_(b), and R_(c) independently represents H, astraight or branched alkyl group having from 1 to about 10 carbon atoms,OCH₃, or halogens.
 17. The composition of claim 12, wherein thecounterion is selected from the group consisting of metals, non-metals,and cations or anions based on either carbon, nitrogen or phosphorus.18. The composition of claim 1, wherein the at least one functionalgroup of the sterically bulky stabilizer is selected from the groupconsisting of sulfonate/sulfonic acid,(thio)carboxylate/(thio)carboxylic acid, phosphonate/phosphonic acid,ammonium and substituted ammonium salts, phosphonium and substitutedphosphonium salts, substituted carbonium salts, substituted aryliumsalts, alkyl/aryl (thio)carboxylate esters, thiol esters, primary andsecondary amides, primary and secondary amines, hydroxyl, ketone,aldehyde, oxime, hydroxylamino, enamines, porphyrins, (phthalo)cyanines,urethane, carbamate, substituted ureas, guanidines and guanidiniumsalts, pyridine and pyridinium salts, imidazolium and (benz)imidazoliumsalts, (benz)imidazolones, pyrrolo, pyrimidine and pyrimidinium salts,pyridinone, piperidine and piperidinium salts, piperazine andpiperazinium salts, triazolo, tetraazolo, oxazole, oxazolines andoxazolinium salts, indoles, indenones, and mixtures thereof.
 19. Thecomposition of claim 1, wherein the sterically bulky stabilizercomprises at least one aliphatic hydrocarbon moiety.
 20. The compositionof claim 1, further comprising adding a surfactant selected from thegroup consisting of rosin-type compounds; acrylic-based polymers;styrene-based copolymers; copolymers of a-olefins; copolymers of vinylpyridine, vinyl imidazole, and vinyl pyrrolidinone; polyestercopolymers; polyamide copolymers; and copolymers of vinyl acetals andvinyl acetates, and mixtures thereof
 21. The composition of claim 1,wherein the non-covalent association between the organic monoazo lakedpigment and the sterically bulky stabilizer compound is at least one ofvan der Waals' forces, ionic bonding, coordination bonding, hydrogenbonding, and aromatic pi-stacking bonding.
 22. The composition of claim1, wherein the nano-sized monoazo laked pigment composition has tunablecoloristic properties as a function of particle size of the nano-sizedparticles.
 23. The composition of claim 1, wherein the sterically bulkystabilizer is selected from the group consisting of the followingcompounds: